Class: BigDecimal

Inherits:
Numeric
  • Object
show all
Defined in:
bigdecimal.c,
lib/bigdecimal/util.rb,
bigdecimal.c

Overview

BigDecimal provides arbitrary-precision floating point decimal arithmetic.

Introduction

Ruby provides built-in support for arbitrary precision integer arithmetic.

For example:

42**13 #=> 1265437718438866624512

BigDecimal provides similar support for very large or very accurate floating point numbers.

Decimal arithmetic is also useful for general calculation, because it provides the correct answers people expect–whereas normal binary floating point arithmetic often introduces subtle errors because of the conversion between base 10 and base 2.

For example, try:

sum = 0
10_000.times do
  sum = sum + 0.0001
end
print sum #=> 0.9999999999999062

and contrast with the output from:

require 'bigdecimal'

sum = BigDecimal("0")
10_000.times do
  sum = sum + BigDecimal("0.0001")
end
print sum #=> 0.1E1

Similarly:

(BigDecimal(“1.2”) - BigDecimal(“1.0”)) == BigDecimal(“0.2”) #=> true

(1.2 - 1.0) == 0.2 #=> false

Special features of accurate decimal arithmetic

Because BigDecimal is more accurate than normal binary floating point arithmetic, it requires some special values.

Infinity

BigDecimal sometimes needs to return infinity, for example if you divide a value by zero.

BigDecimal(“1.0”) / BigDecimal(“0.0”) #=> Infinity BigDecimal(“-1.0”) / BigDecimal(“0.0”) #=> -Infinity

You can represent infinite numbers to BigDecimal using the strings 'Infinity', '+Infinity' and '-Infinity' (case-sensitive)

Not a Number

When a computation results in an undefined value, the special value NaN (for 'not a number') is returned.

Example:

BigDecimal(“0.0”) / BigDecimal(“0.0”) #=> NaN

You can also create undefined values.

NaN is never considered to be the same as any other value, even NaN itself:

n = BigDecimal('NaN') n == 0.0 #=> false n == n #=> false

Positive and negative zero

If a computation results in a value which is too small to be represented as a BigDecimal within the currently specified limits of precision, zero must be returned.

If the value which is too small to be represented is negative, a BigDecimal value of negative zero is returned.

BigDecimal(“1.0”) / BigDecimal(“-Infinity”) #=> -0.0

If the value is positive, a value of positive zero is returned.

BigDecimal(“1.0”) / BigDecimal(“Infinity”) #=> 0.0

(See BigDecimal.mode for how to specify limits of precision.)

Note that -0.0 and 0.0 are considered to be the same for the purposes of comparison.

Note also that in mathematics, there is no particular concept of negative or positive zero; true mathematical zero has no sign.

bigdecimal/util

When you require bigdecimal/util, the #to_d method will be available on BigDecimal and the native Integer, Float, Rational, and String classes:

require 'bigdecimal/util'

42.to_d         # => 0.42e2
0.5.to_d        # => 0.5e0
(2/3r).to_d(3)  # => 0.667e0
"0.5".to_d      # => 0.5e0

License

Copyright (C) 2002 by Shigeo Kobayashi <[email protected]>.

BigDecimal is released under the Ruby and 2-clause BSD licenses. See LICENSE.txt for details.

Maintained by mrkn <[email protected]> and ruby-core members.

Documented by zzak <[email protected]>, mathew <[email protected]>, and many other contributors.

Constant Summary collapse

VERSION =

The version of bigdecimal library

rb_str_new2(RUBY_BIGDECIMAL_VERSION)
BASE =

Base value used in internal calculations. On a 32 bit system, BASE is 10000, indicating that calculation is done in groups of 4 digits. (If it were larger, BASE**2 wouldn't fit in 32 bits, so you couldn't guarantee that two groups could always be multiplied together without overflow.)

INT2FIX((SIGNED_VALUE)VpBaseVal())
EXCEPTION_ALL =

Determines whether overflow, underflow or zero divide result in an exception being thrown. See BigDecimal.mode.

0xff
EXCEPTION_NaN =

Determines what happens when the result of a computation is not a number (NaN). See BigDecimal.mode.

0x02
EXCEPTION_INFINITY =

Determines what happens when the result of a computation is infinity. See BigDecimal.mode.

0x01
EXCEPTION_UNDERFLOW =

Determines what happens when the result of a computation is an underflow (a result too small to be represented). See BigDecimal.mode.

0x04
EXCEPTION_OVERFLOW =

Determines what happens when the result of a computation is an overflow (a result too large to be represented). See BigDecimal.mode.

0x01
EXCEPTION_ZERODIVIDE =

Determines what happens when a division by zero is performed. See BigDecimal.mode.

0x10
ROUND_MODE =

Determines what happens when a result must be rounded in order to fit in the appropriate number of significant digits. See BigDecimal.mode.

0x100
ROUND_UP =

Indicates that values should be rounded away from zero. See BigDecimal.mode.

1
ROUND_DOWN =

Indicates that values should be rounded towards zero. See BigDecimal.mode.

2
ROUND_HALF_UP =

Indicates that digits >= 5 should be rounded up, others rounded down. See BigDecimal.mode.

3
ROUND_HALF_DOWN =

Indicates that digits >= 6 should be rounded up, others rounded down. See BigDecimal.mode.

4
ROUND_CEILING =

Round towards +Infinity. See BigDecimal.mode.

5
ROUND_FLOOR =

Round towards -Infinity. See BigDecimal.mode.

6
ROUND_HALF_EVEN =

Round towards the even neighbor. See BigDecimal.mode.

7
SIGN_NaN =

Indicates that a value is not a number. See BigDecimal.sign.

0
SIGN_POSITIVE_ZERO =

Indicates that a value is +0. See BigDecimal.sign.

1
SIGN_NEGATIVE_ZERO =

Indicates that a value is -0. See BigDecimal.sign.

-1
SIGN_POSITIVE_FINITE =

Indicates that a value is positive and finite. See BigDecimal.sign.

2
SIGN_NEGATIVE_FINITE =

Indicates that a value is negative and finite. See BigDecimal.sign.

-2
SIGN_POSITIVE_INFINITE =

Indicates that a value is positive and infinite. See BigDecimal.sign.

3
SIGN_NEGATIVE_INFINITE =

Indicates that a value is negative and infinite. See BigDecimal.sign.

-3
INFINITY =

Positive infinity value.

f_BigDecimal(1, &arg, rb_cBigDecimal)
NAN =

'Not a Number' value.

f_BigDecimal(1, &arg, rb_cBigDecimal)

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

._load(str) ⇒ Object

Internal method used to provide marshalling support. See the Marshal module.


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# File 'bigdecimal.c', line 538

static VALUE
BigDecimal_load(VALUE self, VALUE str)
{
    ENTER(2);
    Real *pv;
    unsigned char *pch;
    unsigned char ch;
    unsigned long m=0;

    pch = (unsigned char *)StringValueCStr(str);
    /* First get max prec */
    while((*pch) != (unsigned char)'\0' && (ch = *pch++) != (unsigned char)':') {
        if(!ISDIGIT(ch)) {
            rb_raise(rb_eTypeError, "load failed: invalid character in the marshaled string");
        }
        m = m*10 + (unsigned long)(ch-'0');
    }
    if (m > VpBaseFig()) m -= VpBaseFig();
    GUARD_OBJ(pv, VpNewRbClass(m, (char *)pch, self));
    m /= VpBaseFig();
    if (m && pv->MaxPrec > m) {
	pv->MaxPrec = m+1;
    }
    return ToValue(pv);
}

.double_figObject

BigDecimal.double_fig

The BigDecimal.double_fig class method returns the number of digits a Float number is allowed to have. The result depends upon the CPU and OS in use.


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# File 'bigdecimal.c', line 349

static VALUE
BigDecimal_double_fig(VALUE self)
{
    return INT2FIX(VpDblFig());
}

.interpret_loosely(str) ⇒ Object


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# File 'bigdecimal.c', line 2892

static VALUE
BigDecimal_s_interpret_loosely(VALUE klass, VALUE str)
{
    ENTER(1);
    char const *c_str;
    Real *pv;

    c_str = StringValueCStr(str);
    GUARD_OBJ(pv, VpAlloc(0, c_str, 0, 1));
    pv->obj = TypedData_Wrap_Struct(klass, &BigDecimal_data_type, pv);
    RB_OBJ_FREEZE(pv->obj);
    return pv->obj;
}

.limit(*args) ⇒ Object

BigDecimal.limit(digits)

Limit the number of significant digits in newly created BigDecimal numbers to the specified value. Rounding is performed as necessary, as specified by BigDecimal.mode.

A limit of 0, the default, means no upper limit.

The limit specified by this method takes less priority over any limit specified to instance methods such as ceil, floor, truncate, or round.


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# File 'bigdecimal.c', line 2918

static VALUE
BigDecimal_limit(int argc, VALUE *argv, VALUE self)
{
    VALUE  nFig;
    VALUE  nCur = SIZET2NUM(VpGetPrecLimit());

    if (rb_scan_args(argc, argv, "01", &nFig) == 1) {
	int nf;
	if (NIL_P(nFig)) return nCur;
	nf = NUM2INT(nFig);
	if (nf < 0) {
	    rb_raise(rb_eArgError, "argument must be positive");
	}
	VpSetPrecLimit(nf);
    }
    return nCur;
}

.mode(*args) ⇒ Object

BigDecimal.mode(mode, value)

Controls handling of arithmetic exceptions and rounding. If no value is supplied, the current value is returned.

Six values of the mode parameter control the handling of arithmetic exceptions:

BigDecimal::EXCEPTION_NaN BigDecimal::EXCEPTION_INFINITY BigDecimal::EXCEPTION_UNDERFLOW BigDecimal::EXCEPTION_OVERFLOW BigDecimal::EXCEPTION_ZERODIVIDE BigDecimal::EXCEPTION_ALL

For each mode parameter above, if the value set is false, computation continues after an arithmetic exception of the appropriate type. When computation continues, results are as follows:

EXCEPTION_NaN

NaN

EXCEPTION_INFINITY

+Infinity or -Infinity

EXCEPTION_UNDERFLOW

0

EXCEPTION_OVERFLOW

+Infinity or -Infinity

EXCEPTION_ZERODIVIDE

+Infinity or -Infinity

One value of the mode parameter controls the rounding of numeric values: BigDecimal::ROUND_MODE. The values it can take are:

ROUND_UP, :up

round away from zero

ROUND_DOWN, :down, :truncate

round towards zero (truncate)

ROUND_HALF_UP, :half_up, :default

round towards the nearest neighbor, unless both neighbors are equidistant, in which case round away from zero. (default)

ROUND_HALF_DOWN, :half_down

round towards the nearest neighbor, unless both neighbors are equidistant, in which case round towards zero.

ROUND_HALF_EVEN, :half_even, :banker

round towards the nearest neighbor, unless both neighbors are equidistant, in which case round towards the even neighbor (Banker's rounding)

ROUND_CEILING, :ceiling, :ceil

round towards positive infinity (ceil)

ROUND_FLOOR, :floor

round towards negative infinity (floor)


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# File 'bigdecimal.c', line 686

static VALUE
BigDecimal_mode(int argc, VALUE *argv, VALUE self)
{
    VALUE which;
    VALUE val;
    unsigned long f,fo;

    rb_scan_args(argc, argv, "11", &which, &val);
    f = (unsigned long)NUM2INT(which);

    if (f & VP_EXCEPTION_ALL) {
	/* Exception mode setting */
	fo = VpGetException();
	if (val == Qnil) return INT2FIX(fo);
	if (val != Qfalse && val!=Qtrue) {
	    rb_raise(rb_eArgError, "second argument must be true or false");
	    return Qnil; /* Not reached */
	}
	if (f & VP_EXCEPTION_INFINITY) {
	    VpSetException((unsigned short)((val == Qtrue) ? (fo | VP_EXCEPTION_INFINITY) :
			(fo & (~VP_EXCEPTION_INFINITY))));
	}
	fo = VpGetException();
	if (f & VP_EXCEPTION_NaN) {
	    VpSetException((unsigned short)((val == Qtrue) ? (fo | VP_EXCEPTION_NaN) :
			(fo & (~VP_EXCEPTION_NaN))));
	}
	fo = VpGetException();
	if (f & VP_EXCEPTION_UNDERFLOW) {
	    VpSetException((unsigned short)((val == Qtrue) ? (fo | VP_EXCEPTION_UNDERFLOW) :
			(fo & (~VP_EXCEPTION_UNDERFLOW))));
	}
	fo = VpGetException();
	if(f & VP_EXCEPTION_ZERODIVIDE) {
	    VpSetException((unsigned short)((val == Qtrue) ? (fo | VP_EXCEPTION_ZERODIVIDE) :
			(fo & (~VP_EXCEPTION_ZERODIVIDE))));
	}
	fo = VpGetException();
	return INT2FIX(fo);
    }
    if (VP_ROUND_MODE == f) {
	/* Rounding mode setting */
	unsigned short sw;
	fo = VpGetRoundMode();
	if (NIL_P(val)) return INT2FIX(fo);
	sw = check_rounding_mode(val);
	fo = VpSetRoundMode(sw);
	return INT2FIX(fo);
    }
    rb_raise(rb_eTypeError, "first argument for BigDecimal.mode invalid");
    return Qnil;
}

.save_exception_mode { ... } ⇒ Object

Execute the provided block, but preserve the exception mode

BigDecimal.save_exception_mode do
  BigDecimal.mode(BigDecimal::EXCEPTION_OVERFLOW, false)
  BigDecimal.mode(BigDecimal::EXCEPTION_NaN, false)

  BigDecimal(BigDecimal('Infinity'))
  BigDecimal(BigDecimal('-Infinity'))
  BigDecimal(BigDecimal('NaN'))
end

For use with the BigDecimal::EXCEPTION_*

See BigDecimal.mode

Yields:


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# File 'bigdecimal.c', line 2977

static VALUE
BigDecimal_save_exception_mode(VALUE self)
{
    unsigned short const exception_mode = VpGetException();
    int state;
    VALUE ret = rb_protect(rb_yield, Qnil, &state);
    VpSetException(exception_mode);
    if (state) rb_jump_tag(state);
    return ret;
}

.save_limit { ... } ⇒ Object

Execute the provided block, but preserve the precision limit

BigDecimal.limit(100)
puts BigDecimal.limit
BigDecimal.save_limit do
    BigDecimal.limit(200)
    puts BigDecimal.limit
end
puts BigDecimal.limit

Yields:


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# File 'bigdecimal.c', line 3027

static VALUE
BigDecimal_save_limit(VALUE self)
{
    size_t const limit = VpGetPrecLimit();
    int state;
    VALUE ret = rb_protect(rb_yield, Qnil, &state);
    VpSetPrecLimit(limit);
    if (state) rb_jump_tag(state);
    return ret;
}

.save_rounding_mode { ... } ⇒ Object

Execute the provided block, but preserve the rounding mode

BigDecimal.save_rounding_mode do
  BigDecimal.mode(BigDecimal::ROUND_MODE, :up)
  puts BigDecimal.mode(BigDecimal::ROUND_MODE)
end

For use with the BigDecimal::ROUND_*

See BigDecimal.mode

Yields:


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# File 'bigdecimal.c', line 3002

static VALUE
BigDecimal_save_rounding_mode(VALUE self)
{
    unsigned short const round_mode = VpGetRoundMode();
    int state;
    VALUE ret = rb_protect(rb_yield, Qnil, &state);
    VpSetRoundMode(round_mode);
    if (state) rb_jump_tag(state);
    return ret;
}

Instance Method Details

#%Object

%: a%b = a - (a.to_f/b).floor * b


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# File 'bigdecimal.c', line 1557

static VALUE
BigDecimal_mod(VALUE self, VALUE r) /* %: a%b = a - (a.to_f/b).floor * b */
{
    ENTER(3);
    Real *div = NULL, *mod = NULL;

    if (BigDecimal_DoDivmod(self, r, &div, &mod)) {
	SAVE(div); SAVE(mod);
	return ToValue(mod);
    }
    return DoSomeOne(self, r, '%');
}

#*(r) ⇒ Object

call-seq: mult(value, digits)

Multiply by the specified value.

e.g.

c = a.mult(b,n)
c = a * b
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to BigDecimal.mode.


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# File 'bigdecimal.c', line 1376

static VALUE
BigDecimal_mult(VALUE self, VALUE r)
{
    ENTER(5);
    Real *c, *a, *b;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    if (RB_TYPE_P(r, T_FLOAT)) {
        b = GetVpValueWithPrec(r, DBLE_FIG, 1);
    }
    else if (RB_TYPE_P(r, T_RATIONAL)) {
	b = GetVpValueWithPrec(r, a->Prec*VpBaseFig(), 1);
    }
    else {
	b = GetVpValue(r,0);
    }

    if (!b) return DoSomeOne(self, r, '*');
    SAVE(b);

    mx = a->Prec + b->Prec;
    GUARD_OBJ(c, VpCreateRbObject(mx *(VpBaseFig() + 1), "0"));
    VpMult(c, a, b);
    return ToValue(c);
}

#**(n) ⇒ Object

Returns the value raised to the power of n.

See BigDecimal#power.


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# File 'bigdecimal.c', line 2676

static VALUE
BigDecimal_power_op(VALUE self, VALUE exp)
{
    return BigDecimal_power(1, &exp, self);
}

#+(r) ⇒ Object

call-seq: add(value, digits)

Add the specified value.

e.g.

c = a.add(b,n)
c = a + b
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to BigDecimal.mode.


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# File 'bigdecimal.c', line 1055

static VALUE
BigDecimal_add(VALUE self, VALUE r)
{
    ENTER(5);
    Real *c, *a, *b;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    if (RB_TYPE_P(r, T_FLOAT)) {
	b = GetVpValueWithPrec(r, DBLE_FIG, 1);
    }
    else if (RB_TYPE_P(r, T_RATIONAL)) {
	b = GetVpValueWithPrec(r, a->Prec*VpBaseFig(), 1);
    }
    else {
	b = GetVpValue(r, 0);
    }

    if (!b) return DoSomeOne(self,r,'+');
    SAVE(b);

    if (VpIsNaN(b)) return b->obj;
    if (VpIsNaN(a)) return a->obj;

    mx = GetAddSubPrec(a, b);
    if (mx == (size_t)-1L) {
	GUARD_OBJ(c,VpCreateRbObject(VpBaseFig() + 1, "0"));
	VpAddSub(c, a, b, 1);
    }
    else {
	GUARD_OBJ(c, VpCreateRbObject(mx * (VpBaseFig() + 1), "0"));
	if(!mx) {
	    VpSetInf(c, VpGetSign(a));
	}
	else {
	    VpAddSub(c, a, b, 1);
	}
    }
    return ToValue(c);
}

#+Object

Return self.

+BigDecimal('5')  #=> 0.5e1

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# File 'bigdecimal.c', line 1032

static VALUE
BigDecimal_uplus(VALUE self)
{
    return self;
}

#-(r) ⇒ Object

a - b -> bigdecimal

Subtract the specified value.

e.g.

c = a - b

The precision of the result value depends on the type of b.

If b is a Float, the precision of the result is Float::DIG+1.

If b is a BigDecimal, the precision of the result is b's precision of internal representation from platform. So, it's return value is platform dependent.


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# File 'bigdecimal.c', line 1113

static VALUE
BigDecimal_sub(VALUE self, VALUE r)
{
    ENTER(5);
    Real *c, *a, *b;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self,1));
    if (RB_TYPE_P(r, T_FLOAT)) {
	b = GetVpValueWithPrec(r, DBLE_FIG, 1);
    }
    else if (RB_TYPE_P(r, T_RATIONAL)) {
	b = GetVpValueWithPrec(r, a->Prec*VpBaseFig(), 1);
    }
    else {
	b = GetVpValue(r,0);
    }

    if (!b) return DoSomeOne(self,r,'-');
    SAVE(b);

    if (VpIsNaN(b)) return b->obj;
    if (VpIsNaN(a)) return a->obj;

    mx = GetAddSubPrec(a,b);
    if (mx == (size_t)-1L) {
	GUARD_OBJ(c,VpCreateRbObject(VpBaseFig() + 1, "0"));
	VpAddSub(c, a, b, -1);
    }
    else {
	GUARD_OBJ(c,VpCreateRbObject(mx *(VpBaseFig() + 1), "0"));
	if (!mx) {
	    VpSetInf(c,VpGetSign(a));
	}
	else {
	    VpAddSub(c, a, b, -1);
	}
    }
    return ToValue(c);
}

#-Object

Return the negation of self.

-BigDecimal('5')  #=> -0.5e1

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# File 'bigdecimal.c', line 1350

static VALUE
BigDecimal_neg(VALUE self)
{
    ENTER(5);
    Real *c, *a;
    GUARD_OBJ(a, GetVpValue(self, 1));
    GUARD_OBJ(c, VpCreateRbObject(a->Prec *(VpBaseFig() + 1), "0"));
    VpAsgn(c, a, -1);
    return ToValue(c);
}

#/Object

For c = self/r: with round operation


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# File 'bigdecimal.c', line 1445

static VALUE
BigDecimal_div(VALUE self, VALUE r)
/* For c = self/r: with round operation */
{
    ENTER(5);
    Real *c=NULL, *res=NULL, *div = NULL;
    r = BigDecimal_divide(&c, &res, &div, self, r);
    if (!NIL_P(r)) return r; /* coerced by other */
    SAVE(c); SAVE(res); SAVE(div);
    /* a/b = c + r/b */
    /* c xxxxx
       r 00000yyyyy  ==> (y/b)*BASE >= HALF_BASE
     */
    /* Round */
    if (VpHasVal(div)) { /* frac[0] must be zero for NaN,INF,Zero */
	VpInternalRound(c, 0, c->frac[c->Prec-1], (BDIGIT)(VpBaseVal() * (BDIGIT_DBL)res->frac[0] / div->frac[0]));
    }
    return ToValue(c);
}

#<(r) ⇒ Object

a < b

Returns true if a is less than b.

Values may be coerced to perform the comparison (see ==, BigDecimal#coerce).


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# File 'bigdecimal.c', line 1296

static VALUE
BigDecimal_lt(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '<');
}

#<=(r) ⇒ Object

a <= b

Returns true if a is less than or equal to b.

Values may be coerced to perform the comparison (see ==, BigDecimal#coerce).


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# File 'bigdecimal.c', line 1309

static VALUE
BigDecimal_le(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, 'L');
}

#<=>(r) ⇒ Object

The comparison operator. a <=> b is 0 if a == b, 1 if a > b, -1 if a < b.


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# File 'bigdecimal.c', line 1267

static VALUE
BigDecimal_comp(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '*');
}

#==(r) ⇒ Object

Tests for value equality; returns true if the values are equal.

The == and === operators and the eql? method have the same implementation for BigDecimal.

Values may be coerced to perform the comparison:

BigDecimal('1.0') == 1.0  #=> true

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# File 'bigdecimal.c', line 1283

static VALUE
BigDecimal_eq(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '=');
}

#===(r) ⇒ Object

Tests for value equality; returns true if the values are equal.

The == and === operators and the eql? method have the same implementation for BigDecimal.

Values may be coerced to perform the comparison:

BigDecimal('1.0') == 1.0  #=> true

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# File 'bigdecimal.c', line 1283

static VALUE
BigDecimal_eq(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '=');
}

#>(r) ⇒ Object

a > b

Returns true if a is greater than b.

Values may be coerced to perform the comparison (see ==, BigDecimal#coerce).


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# File 'bigdecimal.c', line 1322

static VALUE
BigDecimal_gt(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '>');
}

#>=(r) ⇒ Object

a >= b

Returns true if a is greater than or equal to b.

Values may be coerced to perform the comparison (see ==, BigDecimal#coerce)


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# File 'bigdecimal.c', line 1335

static VALUE
BigDecimal_ge(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, 'G');
}

#_dumpObject

Method used to provide marshalling support.

inf = BigDecimal('Infinity')
  #=> Infinity
BigDecimal._load(inf._dump)
  #=> Infinity

See the Marshal module.


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# File 'bigdecimal.c', line 516

static VALUE
BigDecimal_dump(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real *vp;
    char *psz;
    VALUE dummy;
    volatile VALUE dump;

    rb_scan_args(argc, argv, "01", &dummy);
    GUARD_OBJ(vp,GetVpValue(self, 1));
    dump = rb_str_new(0, VpNumOfChars(vp, "E")+50);
    psz = RSTRING_PTR(dump);
    sprintf(psz, "%"PRIuSIZE":", VpMaxPrec(vp)*VpBaseFig());
    VpToString(vp, psz+strlen(psz), 0, 0);
    rb_str_resize(dump, strlen(psz));
    return dump;
}

#absObject

Returns the absolute value, as a BigDecimal.

BigDecimal('5').abs  #=> 0.5e1
BigDecimal('-3').abs #=> 0.3e1

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# File 'bigdecimal.c', line 1826

static VALUE
BigDecimal_abs(VALUE self)
{
    ENTER(5);
    Real *c, *a;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec *(VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpAsgn(c, a, 1);
    VpChangeSign(c, 1);
    return ToValue(c);
}

#add(b, n) ⇒ Object

call-seq: add(value, digits)

Add the specified value.

e.g.

c = a.add(b,n)
c = a + b
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to BigDecimal.mode.


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# File 'bigdecimal.c', line 1751

static VALUE
BigDecimal_add2(VALUE self, VALUE b, VALUE n)
{
    ENTER(2);
    Real *cv;
    SIGNED_VALUE mx = GetPrecisionInt(n);
    if (mx == 0) return BigDecimal_add(self, b);
    else {
	size_t pl = VpSetPrecLimit(0);
	VALUE   c = BigDecimal_add(self, b);
	VpSetPrecLimit(pl);
	GUARD_OBJ(cv, GetVpValue(c, 1));
	VpLeftRound(cv, VpGetRoundMode(), mx);
	return ToValue(cv);
    }
}

#ceil(*args) ⇒ Object

ceil(n)

Return the smallest integer greater than or equal to the value, as a BigDecimal.

BigDecimal('3.14159').ceil #=> 4 BigDecimal('-9.1').ceil #=> -9

If n is specified and positive, the fractional part of the result has no more than that many digits.

If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.

BigDecimal('3.14159').ceil(3) #=> 3.142 BigDecimal('13345.234').ceil(-2) #=> 13400.0


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# File 'bigdecimal.c', line 2084

static VALUE
BigDecimal_ceil(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real *c, *a;
    int iLoc;
    VALUE vLoc;
    size_t mx, pl = VpSetPrecLimit(0);

    if (rb_scan_args(argc, argv, "01", &vLoc) == 0) {
	iLoc = 0;
    } else {
	iLoc = NUM2INT(vLoc);
    }

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSetPrecLimit(pl);
    VpActiveRound(c, a, VP_ROUND_CEIL, iLoc);
    if (argc == 0) {
	return BigDecimal_to_i(ToValue(c));
    }
    return ToValue(c);
}

#cloneObject


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# File 'bigdecimal.c', line 2698

static VALUE
BigDecimal_clone(VALUE self)
{
  return self;
}

#coerce(other) ⇒ Object

The coerce method provides support for Ruby type coercion. It is not enabled by default.

This means that binary operations like + * / or - can often be performed on a BigDecimal and an object of another type, if the other object can be coerced into a BigDecimal value.

e.g.

a = BigDecimal("1.0")
b = a / 2.0 #=> 0.5

Note that coercing a String to a BigDecimal is not supported by default; it requires a special compile-time option when building Ruby.


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# File 'bigdecimal.c', line 998

static VALUE
BigDecimal_coerce(VALUE self, VALUE other)
{
    ENTER(2);
    VALUE obj;
    Real *b;

    if (RB_TYPE_P(other, T_FLOAT)) {
	GUARD_OBJ(b, GetVpValueWithPrec(other, DBLE_FIG, 1));
	obj = rb_assoc_new(ToValue(b), self);
    }
    else {
	if (RB_TYPE_P(other, T_RATIONAL)) {
	    Real* pv = DATA_PTR(self);
	    GUARD_OBJ(b, GetVpValueWithPrec(other, pv->Prec*VpBaseFig(), 1));
	}
	else {
	    GUARD_OBJ(b, GetVpValue(other, 1));
	}
	obj = rb_assoc_new(b->obj, self);
    }

    return obj;
}

#div(*args) ⇒ Object

call-seq:

div(value, digits)  -> bigdecimal or integer

Divide by the specified value.

digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to BigDecimal.mode.

If digits is 0, the result is the same as for the / operator or #quo.

If digits is not specified, the result is an integer, by analogy with Float#div; see also BigDecimal#divmod.

Examples:

a = BigDecimal("4")
b = BigDecimal("3")

a.div(b, 3)  # => 0.133e1

a.div(b, 0)  # => 0.1333333333333333333e1
a / b        # => 0.1333333333333333333e1
a.quo(b)     # => 0.1333333333333333333e1

a.div(b)     # => 1

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# File 'bigdecimal.c', line 1741

static VALUE
BigDecimal_div3(int argc, VALUE *argv, VALUE self)
{
    VALUE b,n;

    rb_scan_args(argc, argv, "11", &b, &n);

    return BigDecimal_div2(self, b, n);
}

#divmod(r) ⇒ Object

divmod(value)

Divides by the specified value, and returns the quotient and modulus as BigDecimal numbers. The quotient is rounded towards negative infinity.

For example:

require 'bigdecimal'

a = BigDecimal("42")
b = BigDecimal("9")

q, m = a.divmod(b)

c = q * b + m

a == c  #=> true

The quotient q is (a/b).floor, and the modulus is the amount that must be added to q * b to get a.


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# File 'bigdecimal.c', line 1655

static VALUE
BigDecimal_divmod(VALUE self, VALUE r)
{
    ENTER(5);
    Real *div = NULL, *mod = NULL;

    if (BigDecimal_DoDivmod(self, r, &div, &mod)) {
	SAVE(div); SAVE(mod);
	return rb_assoc_new(ToValue(div), ToValue(mod));
    }
    return DoSomeOne(self,r,rb_intern("divmod"));
}

#dupObject


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# File 'bigdecimal.c', line 2698

static VALUE
BigDecimal_clone(VALUE self)
{
  return self;
}

#eql?(r) ⇒ Boolean

Tests for value equality; returns true if the values are equal.

The == and === operators and the eql? method have the same implementation for BigDecimal.

Values may be coerced to perform the comparison:

BigDecimal('1.0') == 1.0  #=> true

Returns:

  • (Boolean)

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# File 'bigdecimal.c', line 1283

static VALUE
BigDecimal_eq(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '=');
}

#exponentObject

Returns the exponent of the BigDecimal number, as an Integer.

If the number can be represented as 0.xxxxxx*10**n where xxxxxx is a string of digits with no leading zeros, then n is the exponent.


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# File 'bigdecimal.c', line 2275

static VALUE
BigDecimal_exponent(VALUE self)
{
    ssize_t e = VpExponent10(GetVpValue(self, 1));
    return SSIZET2NUM(e);
}

#finite?Boolean

Returns True if the value is finite (not NaN or infinite).

Returns:

  • (Boolean)

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# File 'bigdecimal.c', line 829

static VALUE
BigDecimal_IsFinite(VALUE self)
{
    Real *p = GetVpValue(self, 1);
    if (VpIsNaN(p)) return Qfalse;
    if (VpIsInf(p)) return Qfalse;
    return Qtrue;
}

#fixObject

Return the integer part of the number, as a BigDecimal.


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# File 'bigdecimal.c', line 1867

static VALUE
BigDecimal_fix(VALUE self)
{
    ENTER(5);
    Real *c, *a;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec *(VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpActiveRound(c, a, VP_ROUND_DOWN, 0); /* 0: round off */
    return ToValue(c);
}

#floor(*args) ⇒ Object

floor(n)

Return the largest integer less than or equal to the value, as a BigDecimal.

BigDecimal('3.14159').floor #=> 3 BigDecimal('-9.1').floor #=> -10

If n is specified and positive, the fractional part of the result has no more than that many digits.

If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.

BigDecimal('3.14159').floor(3) #=> 3.141 BigDecimal('13345.234').floor(-2) #=> 13300.0


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# File 'bigdecimal.c', line 2037

static VALUE
BigDecimal_floor(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real *c, *a;
    int iLoc;
    VALUE vLoc;
    size_t mx, pl = VpSetPrecLimit(0);

    if (rb_scan_args(argc, argv, "01", &vLoc)==0) {
	iLoc = 0;
    }
    else {
	iLoc = NUM2INT(vLoc);
    }

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSetPrecLimit(pl);
    VpActiveRound(c, a, VP_ROUND_FLOOR, iLoc);
#ifdef BIGDECIMAL_DEBUG
    VPrint(stderr, "floor: c=%\n", c);
#endif
    if (argc == 0) {
	return BigDecimal_to_i(ToValue(c));
    }
    return ToValue(c);
}

#fracObject

Return the fractional part of the number, as a BigDecimal.


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# File 'bigdecimal.c', line 2006

static VALUE
BigDecimal_frac(VALUE self)
{
    ENTER(5);
    Real *c, *a;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpFrac(c, a);
    return ToValue(c);
}

#hashObject

Creates a hash for this BigDecimal.

Two BigDecimals with equal sign, fractional part and exponent have the same hash.


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# File 'bigdecimal.c', line 487

static VALUE
BigDecimal_hash(VALUE self)
{
    ENTER(1);
    Real *p;
    st_index_t hash;

    GUARD_OBJ(p, GetVpValue(self, 1));
    hash = (st_index_t)p->sign;
    /* hash!=2: the case for 0(1),NaN(0) or +-Infinity(3) is sign itself */
    if(hash == 2 || hash == (st_index_t)-2) {
	hash ^= rb_memhash(p->frac, sizeof(BDIGIT)*p->Prec);
	hash += p->exponent;
    }
    return ST2FIX(hash);
}

#infinite?Boolean

Returns nil, -1, or 1 depending on whether the value is finite, -Infinity, or Infinity.

Returns:

  • (Boolean)

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# File 'bigdecimal.c', line 819

static VALUE
BigDecimal_IsInfinite(VALUE self)
{
    Real *p = GetVpValue(self, 1);
    if (VpIsPosInf(p)) return INT2FIX(1);
    if (VpIsNegInf(p)) return INT2FIX(-1);
    return Qnil;
}

#inspectObject

Returns a string representation of self.

BigDecimal("1234.5678").inspect
  #=> "0.12345678e4"

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# File 'bigdecimal.c', line 2287

static VALUE
BigDecimal_inspect(VALUE self)
{
    ENTER(5);
    Real *vp;
    volatile VALUE str;
    size_t nc;

    GUARD_OBJ(vp, GetVpValue(self, 1));
    nc = VpNumOfChars(vp, "E");

    str = rb_str_new(0, nc);
    VpToString(vp, RSTRING_PTR(str), 0, 0);
    rb_str_resize(str, strlen(RSTRING_PTR(str)));
    return str;
}

#moduloObject

%: a%b = a - (a.to_f/b).floor * b


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# File 'bigdecimal.c', line 1557

static VALUE
BigDecimal_mod(VALUE self, VALUE r) /* %: a%b = a - (a.to_f/b).floor * b */
{
    ENTER(3);
    Real *div = NULL, *mod = NULL;

    if (BigDecimal_DoDivmod(self, r, &div, &mod)) {
	SAVE(div); SAVE(mod);
	return ToValue(mod);
    }
    return DoSomeOne(self, r, '%');
}

#mult(b, n) ⇒ Object

call-seq: mult(value, digits)

Multiply by the specified value.

e.g.

c = a.mult(b,n)
c = a * b
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to BigDecimal.mode.


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# File 'bigdecimal.c', line 1799

static VALUE
BigDecimal_mult2(VALUE self, VALUE b, VALUE n)
{
    ENTER(2);
    Real *cv;
    SIGNED_VALUE mx = GetPrecisionInt(n);
    if (mx == 0) return BigDecimal_mult(self, b);
    else {
	size_t pl = VpSetPrecLimit(0);
	VALUE   c = BigDecimal_mult(self, b);
	VpSetPrecLimit(pl);
	GUARD_OBJ(cv, GetVpValue(c, 1));
	VpLeftRound(cv, VpGetRoundMode(), mx);
	return ToValue(cv);
    }
}

#n_significant_digitsObject


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# File 'bigdecimal.c', line 453

static VALUE
BigDecimal_n_significant_digits(VALUE self)
{
    ENTER(1);

    Real *p;
    GUARD_OBJ(p, GetVpValue(self, 1));

    ssize_t n = p->Prec;
    while (n > 0 && p->frac[n-1] == 0) --n;
    if (n <= 0) {
        return INT2FIX(0);
    }

    int nlz, ntz;

    BDIGIT x = p->frac[0];
    for (nlz = BASE_FIG; x > 0; x /= 10) --nlz;

    x = p->frac[n-1];
    for (ntz = 0; x > 0 && x % 10 == 0; x /= 10) ++ntz;

    ssize_t n_digits = BASE_FIG * n - nlz - ntz;
    return SSIZET2NUM(n_digits);
}

#nan?Boolean

Returns True if the value is Not a Number.

Returns:

  • (Boolean)

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# File 'bigdecimal.c', line 808

static VALUE
BigDecimal_IsNaN(VALUE self)
{
    Real *p = GetVpValue(self, 1);
    if (VpIsNaN(p))  return Qtrue;
    return Qfalse;
}

#nonzero?Boolean

Returns self if the value is non-zero, nil otherwise.

Returns:

  • (Boolean)

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# File 'bigdecimal.c', line 1257

static VALUE
BigDecimal_nonzero(VALUE self)
{
    Real *a = GetVpValue(self, 1);
    return VpIsZero(a) ? Qnil : self;
}

#power(*args) ⇒ Object

power(n) power(n, prec)

Returns the value raised to the power of n.

Note that n must be an Integer.

Also available as the operator **.


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# File 'bigdecimal.c', line 2430

static VALUE
BigDecimal_power(int argc, VALUE*argv, VALUE self)
{
    ENTER(5);
    VALUE vexp, prec;
    Real* exp = NULL;
    Real *x, *y;
    ssize_t mp, ma, n;
    SIGNED_VALUE int_exp;
    double d;

    rb_scan_args(argc, argv, "11", &vexp, &prec);

    GUARD_OBJ(x, GetVpValue(self, 1));
    n = NIL_P(prec) ? (ssize_t)(x->Prec*VpBaseFig()) : NUM2SSIZET(prec);

    if (VpIsNaN(x)) {
	y = VpCreateRbObject(n, "0");
	RB_GC_GUARD(y->obj);
	VpSetNaN(y);
	return ToValue(y);
    }

  retry:
    switch (TYPE(vexp)) {
      case T_FIXNUM:
	break;

      case T_BIGNUM:
	break;

      case T_FLOAT:
	d = RFLOAT_VALUE(vexp);
	if (d == round(d)) {
	    if (FIXABLE(d)) {
		vexp = LONG2FIX((long)d);
	    }
	    else {
		vexp = rb_dbl2big(d);
	    }
	    goto retry;
	}
        if (NIL_P(prec)) {
            n += DBLE_FIG;
        }
        exp = GetVpValueWithPrec(vexp, DBLE_FIG, 1);
	break;

      case T_RATIONAL:
	if (is_zero(rb_rational_num(vexp))) {
	    if (is_positive(vexp)) {
		vexp = INT2FIX(0);
		goto retry;
	    }
	}
	else if (is_one(rb_rational_den(vexp))) {
	    vexp = rb_rational_num(vexp);
	    goto retry;
	}
	exp = GetVpValueWithPrec(vexp, n, 1);
        if (NIL_P(prec)) {
            n += n;
        }
	break;

      case T_DATA:
	if (is_kind_of_BigDecimal(vexp)) {
	    VALUE zero = INT2FIX(0);
	    VALUE rounded = BigDecimal_round(1, &zero, vexp);
	    if (RTEST(BigDecimal_eq(vexp, rounded))) {
		vexp = BigDecimal_to_i(vexp);
		goto retry;
	    }
            if (NIL_P(prec)) {
                GUARD_OBJ(y, GetVpValue(vexp, 1));
                n += y->Prec*VpBaseFig();
            }
	    exp = DATA_PTR(vexp);
	    break;
	}
	/* fall through */
      default:
	rb_raise(rb_eTypeError,
		 "wrong argument type %"PRIsVALUE" (expected scalar Numeric)",
		 RB_OBJ_CLASSNAME(vexp));
    }

    if (VpIsZero(x)) {
	if (is_negative(vexp)) {
	    y = VpCreateRbObject(n, "#0");
	    RB_GC_GUARD(y->obj);
	    if (BIGDECIMAL_NEGATIVE_P(x)) {
		if (is_integer(vexp)) {
		    if (is_even(vexp)) {
			/* (-0) ** (-even_integer)  -> Infinity */
			VpSetPosInf(y);
		    }
		    else {
			/* (-0) ** (-odd_integer)  -> -Infinity */
			VpSetNegInf(y);
		    }
		}
		else {
		    /* (-0) ** (-non_integer)  -> Infinity */
		    VpSetPosInf(y);
		}
	    }
	    else {
		/* (+0) ** (-num)  -> Infinity */
		VpSetPosInf(y);
	    }
	    return ToValue(y);
	}
	else if (is_zero(vexp)) {
	    return ToValue(VpCreateRbObject(n, "1"));
	}
	else {
	    return ToValue(VpCreateRbObject(n, "0"));
	}
    }

    if (is_zero(vexp)) {
	return ToValue(VpCreateRbObject(n, "1"));
    }
    else if (is_one(vexp)) {
	return self;
    }

    if (VpIsInf(x)) {
	if (is_negative(vexp)) {
	    if (BIGDECIMAL_NEGATIVE_P(x)) {
		if (is_integer(vexp)) {
		    if (is_even(vexp)) {
			/* (-Infinity) ** (-even_integer) -> +0 */
			return ToValue(VpCreateRbObject(n, "0"));
		    }
		    else {
			/* (-Infinity) ** (-odd_integer) -> -0 */
			return ToValue(VpCreateRbObject(n, "-0"));
		    }
		}
		else {
		    /* (-Infinity) ** (-non_integer) -> -0 */
		    return ToValue(VpCreateRbObject(n, "-0"));
		}
	    }
	    else {
		return ToValue(VpCreateRbObject(n, "0"));
	    }
	}
	else {
	    y = VpCreateRbObject(n, "0");
	    if (BIGDECIMAL_NEGATIVE_P(x)) {
		if (is_integer(vexp)) {
		    if (is_even(vexp)) {
			VpSetPosInf(y);
		    }
		    else {
			VpSetNegInf(y);
		    }
		}
		else {
		    /* TODO: support complex */
		    rb_raise(rb_eMathDomainError,
			     "a non-integral exponent for a negative base");
		}
	    }
	    else {
		VpSetPosInf(y);
	    }
	    return ToValue(y);
	}
    }

    if (exp != NULL) {
	return rmpd_power_by_big_decimal(x, exp, n);
    }
    else if (RB_TYPE_P(vexp, T_BIGNUM)) {
	VALUE abs_value = BigDecimal_abs(self);
	if (is_one(abs_value)) {
	    return ToValue(VpCreateRbObject(n, "1"));
	}
	else if (RTEST(rb_funcall(abs_value, '<', 1, INT2FIX(1)))) {
	    if (is_negative(vexp)) {
		y = VpCreateRbObject(n, "0");
		if (is_even(vexp)) {
		    VpSetInf(y, VpGetSign(x));
		}
		else {
		    VpSetInf(y, -VpGetSign(x));
		}
		return ToValue(y);
	    }
	    else if (BIGDECIMAL_NEGATIVE_P(x) && is_even(vexp)) {
		return ToValue(VpCreateRbObject(n, "-0"));
	    }
	    else {
		return ToValue(VpCreateRbObject(n, "0"));
	    }
	}
	else {
	    if (is_positive(vexp)) {
		y = VpCreateRbObject(n, "0");
		if (is_even(vexp)) {
		    VpSetInf(y, VpGetSign(x));
		}
		else {
		    VpSetInf(y, -VpGetSign(x));
		}
		return ToValue(y);
	    }
	    else if (BIGDECIMAL_NEGATIVE_P(x) && is_even(vexp)) {
		return ToValue(VpCreateRbObject(n, "-0"));
	    }
	    else {
		return ToValue(VpCreateRbObject(n, "0"));
	    }
	}
    }

    int_exp = FIX2LONG(vexp);
    ma = int_exp;
    if (ma <  0) ma = -ma;
    if (ma == 0) ma = 1;

    if (VpIsDef(x)) {
	mp = x->Prec * (VpBaseFig() + 1);
	GUARD_OBJ(y, VpCreateRbObject(mp * (ma + 1), "0"));
    }
    else {
	GUARD_OBJ(y, VpCreateRbObject(1, "0"));
    }
    VpPower(y, x, int_exp);
    if (!NIL_P(prec) && VpIsDef(y)) {
	VpMidRound(y, VpGetRoundMode(), n);
    }
    return ToValue(y);
}

#precisionObject

Returns the number of decimal digits in this number.

Example:

BigDecimal("0").precision  # => 0
BigDecimal("1").precision  # => 1
BigDecimal("-1e20").precision  # => 21
BigDecimal("1e-20").precision  # => 20
BigDecimal("Infinity").precision  # => 0
BigDecimal("-Infinity").precision  # => 0
BigDecimal("NaN").precision  # => 0

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# File 'bigdecimal.c', line 402

static VALUE
BigDecimal_precision(VALUE self)
{
    ENTER(1);

    Real *p;
    GUARD_OBJ(p, GetVpValue(self, 1));

    /*
     * The most significant digit is frac[0], and the least significant digit is frac[Prec-1].
     * When the exponent is zero, the decimal point is located just before frac[0].
     * When the exponent is negative, the decimal point moves to leftward.
     * Conversely, when the exponent is positive, the decimal point moves to rightward.
     *
     *    | frac[0] frac[1] frac[2] . frac[3] frac[4] ... frac[Prec-1]
     *    |------------------------> exponent == 3
     */

    ssize_t ex = p->exponent;
    ssize_t precision = 0;
    if (ex < 0) {
        precision = (-ex + 1) * BASE_FIG;  /* 1 is for p->frac[0] */
        ex = 0;
    }
    else if (p->Prec > 0) {
        BDIGIT x = p->frac[0];
        for (precision = 0; x > 0; x /= 10) {
            ++precision;
        }
    }

    if (ex > (ssize_t)p->Prec) {
        precision += (ex - 1) * BASE_FIG;
    }
    else if (p->Prec > 0) {
        ssize_t n = (ssize_t)p->Prec - 1;
        while (n > 0 && p->frac[n] == 0) --n;

        precision += n * BASE_FIG;

        if (ex < (ssize_t)p->Prec) {
            BDIGIT x = p->frac[n];
            for (; x > 0 && x % 10 == 0; x /= 10) {
                --precision;
            }
        }
    }

    return SSIZET2NUM(precision);
}

#precsArray

Returns an Array of two Integer values that represent platform-dependent internal storage properties.

This method is deprecated and will be removed in the future. Instead, use BigDecimal#n_significant_digits for obtaining the number of significant digits in scientific notation, and BigDecimal#precision for obtaining the number of digits in decimal notation.

BigDecimal('5').precs #=> [9, 18]

Returns:

  • (Array)

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# File 'bigdecimal.c', line 369

static VALUE
BigDecimal_prec(VALUE self)
{
    ENTER(1);
    Real *p;
    VALUE obj;

    rb_category_warn(RB_WARN_CATEGORY_DEPRECATED,
                     "BigDecimal#precs is deprecated and will be removed in the future; "
                     "use BigDecimal#precision instead.");

    GUARD_OBJ(p, GetVpValue(self, 1));
    obj = rb_assoc_new(SIZET2NUM(p->Prec*VpBaseFig()),
		       SIZET2NUM(p->MaxPrec*VpBaseFig()));
    return obj;
}

#quoObject

For c = self/r: with round operation


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# File 'bigdecimal.c', line 1445

static VALUE
BigDecimal_div(VALUE self, VALUE r)
/* For c = self/r: with round operation */
{
    ENTER(5);
    Real *c=NULL, *res=NULL, *div = NULL;
    r = BigDecimal_divide(&c, &res, &div, self, r);
    if (!NIL_P(r)) return r; /* coerced by other */
    SAVE(c); SAVE(res); SAVE(div);
    /* a/b = c + r/b */
    /* c xxxxx
       r 00000yyyyy  ==> (y/b)*BASE >= HALF_BASE
     */
    /* Round */
    if (VpHasVal(div)) { /* frac[0] must be zero for NaN,INF,Zero */
	VpInternalRound(c, 0, c->frac[c->Prec-1], (BDIGIT)(VpBaseVal() * (BDIGIT_DBL)res->frac[0] / div->frac[0]));
    }
    return ToValue(c);
}

#remainderObject

remainder


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# File 'bigdecimal.c', line 1623

static VALUE
BigDecimal_remainder(VALUE self, VALUE r) /* remainder */
{
    VALUE  f;
    Real  *d, *rv = 0;
    f = BigDecimal_divremain(self, r, &d, &rv);
    if (!NIL_P(f)) return f;
    return ToValue(rv);
}

#round(*args) ⇒ Object

round(n, mode)

Round to the nearest integer (by default), returning the result as a BigDecimal if n is specified, or as an Integer if it isn't.

BigDecimal('3.14159').round #=> 3 BigDecimal('8.7').round #=> 9 BigDecimal('-9.9').round #=> -10

BigDecimal('3.14159').round(2).class.name #=> “BigDecimal” BigDecimal('3.14159').round.class.name #=> “Integer”

If n is specified and positive, the fractional part of the result has no more than that many digits.

If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result, and return value will be an Integer.

BigDecimal('3.14159').round(3) #=> 3.142 BigDecimal('13345.234').round(-2) #=> 13300

The value of the optional mode argument can be used to determine how rounding is performed; see BigDecimal.mode.


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# File 'bigdecimal.c', line 1906

static VALUE
BigDecimal_round(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real   *c, *a;
    int    iLoc = 0;
    VALUE  vLoc;
    VALUE  vRound;
    int    round_to_int = 0;
    size_t mx, pl;

    unsigned short sw = VpGetRoundMode();

    switch (rb_scan_args(argc, argv, "02", &vLoc, &vRound)) {
      case 0:
	iLoc = 0;
        round_to_int = 1;
	break;
      case 1:
        if (RB_TYPE_P(vLoc, T_HASH)) {
	    sw = check_rounding_mode_option(vLoc);
	}
	else {
	    iLoc = NUM2INT(vLoc);
            if (iLoc < 1) round_to_int = 1;
	}
	break;
      case 2:
	iLoc = NUM2INT(vLoc);
	if (RB_TYPE_P(vRound, T_HASH)) {
	    sw = check_rounding_mode_option(vRound);
	}
	else {
	    sw = check_rounding_mode(vRound);
	}
	break;
      default:
	break;
    }

    pl = VpSetPrecLimit(0);
    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSetPrecLimit(pl);
    VpActiveRound(c, a, sw, iLoc);
    if (round_to_int) {
	return BigDecimal_to_i(ToValue(c));
    }
    return ToValue(c);
}

#signObject

Returns the sign of the value.

Returns a positive value if > 0, a negative value if < 0, and a zero if == 0.

The specific value returned indicates the type and sign of the BigDecimal, as follows:

BigDecimal::SIGN_NaN

value is Not a Number

BigDecimal::SIGN_POSITIVE_ZERO

value is +0

BigDecimal::SIGN_NEGATIVE_ZERO

value is -0

BigDecimal::SIGN_POSITIVE_INFINITE

value is +Infinity

BigDecimal::SIGN_NEGATIVE_INFINITE

value is -Infinity

BigDecimal::SIGN_POSITIVE_FINITE

value is positive

BigDecimal::SIGN_NEGATIVE_FINITE

value is negative


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# File 'bigdecimal.c', line 2952

static VALUE
BigDecimal_sign(VALUE self)
{ /* sign */
    int s = GetVpValue(self, 1)->sign;
    return INT2FIX(s);
}

#splitObject

Splits a BigDecimal number into four parts, returned as an array of values.

The first value represents the sign of the BigDecimal, and is -1 or 1, or 0 if the BigDecimal is Not a Number.

The second value is a string representing the significant digits of the BigDecimal, with no leading zeros.

The third value is the base used for arithmetic (currently always 10) as an Integer.

The fourth value is an Integer exponent.

If the BigDecimal can be represented as 0.xxxxxx*10**n, then xxxxxx is the string of significant digits with no leading zeros, and n is the exponent.

From these values, you can translate a BigDecimal to a float as follows:

sign, significant_digits, base, exponent = a.split
f = sign * "0.#{significant_digits}".to_f * (base ** exponent)

(Note that the to_f method is provided as a more convenient way to translate a BigDecimal to a Float.)


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# File 'bigdecimal.c', line 2238

static VALUE
BigDecimal_split(VALUE self)
{
    ENTER(5);
    Real *vp;
    VALUE obj,str;
    ssize_t e, s;
    char *psz1;

    GUARD_OBJ(vp, GetVpValue(self, 1));
    str = rb_str_new(0, VpNumOfChars(vp, "E"));
    psz1 = RSTRING_PTR(str);
    VpSzMantissa(vp, psz1);
    s = 1;
    if(psz1[0] == '-') {
	size_t len = strlen(psz1 + 1);

	memmove(psz1, psz1 + 1, len);
	psz1[len] = '\0';
        s = -1;
    }
    if (psz1[0] == 'N') s = 0; /* NaN */
    e = VpExponent10(vp);
    obj = rb_ary_new2(4);
    rb_ary_push(obj, INT2FIX(s));
    rb_ary_push(obj, str);
    rb_str_resize(str, strlen(psz1));
    rb_ary_push(obj, INT2FIX(10));
    rb_ary_push(obj, SSIZET2NUM(e));
    return obj;
}

#sqrt(nFig) ⇒ Object

sqrt(n)

Returns the square root of the value.

Result has at least n significant digits.


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# File 'bigdecimal.c', line 1848

static VALUE
BigDecimal_sqrt(VALUE self, VALUE nFig)
{
    ENTER(5);
    Real *c, *a;
    size_t mx, n;

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);

    n = GetPrecisionInt(nFig) + VpDblFig() + BASE_FIG;
    if (mx <= n) mx = n;
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSqrt(c, a);
    return ToValue(c);
}

#sub(b, n) ⇒ Object

sub(value, digits) -> bigdecimal

Subtract the specified value.

e.g.

c = a.sub(b,n)
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to BigDecimal.mode.


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# File 'bigdecimal.c', line 1781

static VALUE
BigDecimal_sub2(VALUE self, VALUE b, VALUE n)
{
    ENTER(2);
    Real *cv;
    SIGNED_VALUE mx = GetPrecisionInt(n);
    if (mx == 0) return BigDecimal_sub(self, b);
    else {
	size_t pl = VpSetPrecLimit(0);
	VALUE   c = BigDecimal_sub(self, b);
	VpSetPrecLimit(pl);
	GUARD_OBJ(cv, GetVpValue(c, 1));
	VpLeftRound(cv, VpGetRoundMode(), mx);
	return ToValue(cv);
    }
}

#to_dObject

call-seq:

a.to_d -> bigdecimal

Returns self.

require 'bigdecimal/util'

d = BigDecimal("3.14")
d.to_d                       # => 0.314e1

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# File 'lib/bigdecimal/util.rb', line 106

def to_d
  self
end

#to_digitsObject

call-seq:

a.to_digits -> string

Converts a BigDecimal to a String of the form “nnnnnn.mmm”. This method is deprecated; use BigDecimal#to_s(“F”) instead.

require 'bigdecimal/util'

d = BigDecimal("3.14")
d.to_digits                  # => "3.14"

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# File 'lib/bigdecimal/util.rb', line 86

def to_digits
  if self.nan? || self.infinite? || self.zero?
    self.to_s
  else
    i       = self.to_i.to_s
    _,f,_,z = self.frac.split
    i + "." + ("0"*(-z)) + f
  end
end

#to_fObject

Returns a new Float object having approximately the same value as the BigDecimal number. Normal accuracy limits and built-in errors of binary Float arithmetic apply.


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# File 'bigdecimal.c', line 905

static VALUE
BigDecimal_to_f(VALUE self)
{
    ENTER(1);
    Real *p;
    double d;
    SIGNED_VALUE e;
    char *buf;
    volatile VALUE str;

    GUARD_OBJ(p, GetVpValue(self, 1));
    if (VpVtoD(&d, &e, p) != 1)
	return rb_float_new(d);
    if (e > (SIGNED_VALUE)(DBL_MAX_10_EXP+BASE_FIG))
	goto overflow;
    if (e < (SIGNED_VALUE)(DBL_MIN_10_EXP-BASE_FIG))
	goto underflow;

    str = rb_str_new(0, VpNumOfChars(p, "E"));
    buf = RSTRING_PTR(str);
    VpToString(p, buf, 0, 0);
    errno = 0;
    d = strtod(buf, 0);
    if (errno == ERANGE) {
	if (d == 0.0) goto underflow;
	if (fabs(d) >= HUGE_VAL) goto overflow;
    }
    return rb_float_new(d);

overflow:
    VpException(VP_EXCEPTION_OVERFLOW, "BigDecimal to Float conversion", 0);
    if (BIGDECIMAL_NEGATIVE_P(p))
	return rb_float_new(VpGetDoubleNegInf());
    else
	return rb_float_new(VpGetDoublePosInf());

underflow:
    VpException(VP_EXCEPTION_UNDERFLOW, "BigDecimal to Float conversion", 0);
    if (BIGDECIMAL_NEGATIVE_P(p))
	return rb_float_new(-0.0);
    else
	return rb_float_new(0.0);
}

#to_iObject

Returns the value as an Integer.

If the BigDecimal is infinity or NaN, raises FloatDomainError.


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# File 'bigdecimal.c', line 858

static VALUE
BigDecimal_to_i(VALUE self)
{
    ENTER(5);
    ssize_t e, nf;
    Real *p;

    GUARD_OBJ(p, GetVpValue(self, 1));
    BigDecimal_check_num(p);

    e = VpExponent10(p);
    if (e <= 0) return INT2FIX(0);
    nf = VpBaseFig();
    if (e <= nf) {
        return LONG2NUM((long)(VpGetSign(p) * (BDIGIT_DBL_SIGNED)p->frac[0]));
    }
    else {
	VALUE a = BigDecimal_split(self);
	VALUE digits = RARRAY_AREF(a, 1);
	VALUE numerator = rb_funcall(digits, rb_intern("to_i"), 0);
	VALUE ret;
	ssize_t dpower = e - (ssize_t)RSTRING_LEN(digits);

	if (BIGDECIMAL_NEGATIVE_P(p)) {
	    numerator = rb_funcall(numerator, '*', 1, INT2FIX(-1));
	}
	if (dpower < 0) {
	    ret = rb_funcall(numerator, rb_intern("div"), 1,
			      rb_funcall(INT2FIX(10), rb_intern("**"), 1,
					 INT2FIX(-dpower)));
	}
	else {
	    ret = rb_funcall(numerator, '*', 1,
			     rb_funcall(INT2FIX(10), rb_intern("**"), 1,
					INT2FIX(dpower)));
	}
	if (RB_TYPE_P(ret, T_FLOAT)) {
	    rb_raise(rb_eFloatDomainError, "Infinity");
	}
	return ret;
    }
}

#to_intObject

Returns the value as an Integer.

If the BigDecimal is infinity or NaN, raises FloatDomainError.


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# File 'bigdecimal.c', line 858

static VALUE
BigDecimal_to_i(VALUE self)
{
    ENTER(5);
    ssize_t e, nf;
    Real *p;

    GUARD_OBJ(p, GetVpValue(self, 1));
    BigDecimal_check_num(p);

    e = VpExponent10(p);
    if (e <= 0) return INT2FIX(0);
    nf = VpBaseFig();
    if (e <= nf) {
        return LONG2NUM((long)(VpGetSign(p) * (BDIGIT_DBL_SIGNED)p->frac[0]));
    }
    else {
	VALUE a = BigDecimal_split(self);
	VALUE digits = RARRAY_AREF(a, 1);
	VALUE numerator = rb_funcall(digits, rb_intern("to_i"), 0);
	VALUE ret;
	ssize_t dpower = e - (ssize_t)RSTRING_LEN(digits);

	if (BIGDECIMAL_NEGATIVE_P(p)) {
	    numerator = rb_funcall(numerator, '*', 1, INT2FIX(-1));
	}
	if (dpower < 0) {
	    ret = rb_funcall(numerator, rb_intern("div"), 1,
			      rb_funcall(INT2FIX(10), rb_intern("**"), 1,
					 INT2FIX(-dpower)));
	}
	else {
	    ret = rb_funcall(numerator, '*', 1,
			     rb_funcall(INT2FIX(10), rb_intern("**"), 1,
					INT2FIX(dpower)));
	}
	if (RB_TYPE_P(ret, T_FLOAT)) {
	    rb_raise(rb_eFloatDomainError, "Infinity");
	}
	return ret;
    }
}

#to_rObject

Converts a BigDecimal to a Rational.


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# File 'bigdecimal.c', line 952

static VALUE
BigDecimal_to_r(VALUE self)
{
    Real *p;
    ssize_t sign, power, denomi_power;
    VALUE a, digits, numerator;

    p = GetVpValue(self, 1);
    BigDecimal_check_num(p);

    sign = VpGetSign(p);
    power = VpExponent10(p);
    a = BigDecimal_split(self);
    digits = RARRAY_AREF(a, 1);
    denomi_power = power - RSTRING_LEN(digits);
    numerator = rb_funcall(digits, rb_intern("to_i"), 0);

    if (sign < 0) {
	numerator = rb_funcall(numerator, '*', 1, INT2FIX(-1));
    }
    if (denomi_power < 0) {
	return rb_Rational(numerator,
			   rb_funcall(INT2FIX(10), rb_intern("**"), 1,
				      INT2FIX(-denomi_power)));
    }
    else {
	return rb_Rational1(rb_funcall(numerator, '*', 1,
				       rb_funcall(INT2FIX(10), rb_intern("**"), 1,
						  INT2FIX(denomi_power))));
    }
}

#to_s(*args) ⇒ Object

to_s(s)

Converts the value to a string.

The default format looks like 0.xxxxEnn.

The optional parameter s consists of either an integer; or an optional '+' or ' ', followed by an optional number, followed by an optional 'E' or 'F'.

If there is a '+' at the start of s, positive values are returned with a leading '+'.

A space at the start of s returns positive values with a leading space.

If s contains a number, a space is inserted after each group of that many fractional digits.

If s ends with an 'E', engineering notation (0.xxxxEnn) is used.

If s ends with an 'F', conventional floating point notation is used.

Examples:

BigDecimal('-123.45678901234567890').to_s('5F')
  #=> '-123.45678 90123 45678 9'

BigDecimal('123.45678901234567890').to_s('+8F')
  #=> '+123.45678901 23456789'

BigDecimal('123.45678901234567890').to_s(' F')
  #=> ' 123.4567890123456789'

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# File 'bigdecimal.c', line 2143

static VALUE
BigDecimal_to_s(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    int   fmt = 0;   /* 0: E format, 1: F format */
    int   fPlus = 0; /* 0: default, 1: set ' ' before digits, 2: set '+' before digits. */
    Real  *vp;
    volatile VALUE str;
    char  *psz;
    char   ch;
    size_t nc, mc = 0;
    SIGNED_VALUE m;
    VALUE  f;

    GUARD_OBJ(vp, GetVpValue(self, 1));

    if (rb_scan_args(argc, argv, "01", &f) == 1) {
	if (RB_TYPE_P(f, T_STRING)) {
	    psz = StringValueCStr(f);
	    if (*psz == ' ') {
		fPlus = 1;
		psz++;
	    }
	    else if (*psz == '+') {
		fPlus = 2;
		psz++;
	    }
	    while ((ch = *psz++) != 0) {
		if (ISSPACE(ch)) {
		    continue;
		}
		if (!ISDIGIT(ch)) {
		    if (ch == 'F' || ch == 'f') {
			fmt = 1; /* F format */
		    }
		    break;
		}
		mc = mc*10 + ch - '0';
	    }
	}
	else {
	    m = NUM2INT(f);
	    if (m <= 0) {
		rb_raise(rb_eArgError, "argument must be positive");
	    }
	    mc = (size_t)m;
	}
    }
    if (fmt) {
	nc = VpNumOfChars(vp, "F");
    }
    else {
	nc = VpNumOfChars(vp, "E");
    }
    if (mc > 0) {
	nc += (nc + mc - 1) / mc + 1;
    }

    str = rb_usascii_str_new(0, nc);
    psz = RSTRING_PTR(str);

    if (fmt) {
	VpToFString(vp, psz, mc, fPlus);
    }
    else {
	VpToString (vp, psz, mc, fPlus);
    }
    rb_str_resize(str, strlen(psz));
    return str;
}

#truncate(*args) ⇒ Object

truncate(n)

Truncate to the nearest integer (by default), returning the result as a BigDecimal.

BigDecimal('3.14159').truncate #=> 3 BigDecimal('8.7').truncate #=> 8 BigDecimal('-9.9').truncate #=> -9

If n is specified and positive, the fractional part of the result has no more than that many digits.

If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.

BigDecimal('3.14159').truncate(3) #=> 3.141 BigDecimal('13345.234').truncate(-2) #=> 13300.0


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# File 'bigdecimal.c', line 1977

static VALUE
BigDecimal_truncate(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real *c, *a;
    int iLoc;
    VALUE vLoc;
    size_t mx, pl = VpSetPrecLimit(0);

    if (rb_scan_args(argc, argv, "01", &vLoc) == 0) {
	iLoc = 0;
    }
    else {
	iLoc = NUM2INT(vLoc);
    }

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSetPrecLimit(pl);
    VpActiveRound(c, a, VP_ROUND_DOWN, iLoc); /* 0: truncate */
    if (argc == 0) {
	return BigDecimal_to_i(ToValue(c));
    }
    return ToValue(c);
}

#zero?Boolean

Returns True if the value is zero.

Returns:

  • (Boolean)

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# File 'bigdecimal.c', line 1249

static VALUE
BigDecimal_zero(VALUE self)
{
    Real *a = GetVpValue(self, 1);
    return VpIsZero(a) ? Qtrue : Qfalse;
}