Module: Comparable

Included in:
File::Stat, Numeric, String, Symbol, Time
Defined in:
compar.c

Overview

The Comparable mixin is used by classes whose objects may be ordered. The class must define the <=> operator, which compares the receiver against another object, returning -1, 0, or +1 depending on whether the receiver is less than, equal to, or greater than the other object. If the other object is not comparable then the <=> operator should return nil. Comparable uses <=> to implement the conventional comparison operators (<, <=, ==, >=, and >) and the method between?.

class SizeMatters
  include Comparable
  attr :str
  def <=>(anOther)
    str.size <=> anOther.str.size
  end
  def initialize(str)
    @str = str
  end
  def inspect
    @str
  end
end

s1 = SizeMatters.new("Z")
s2 = SizeMatters.new("YY")
s3 = SizeMatters.new("XXX")
s4 = SizeMatters.new("WWWW")
s5 = SizeMatters.new("VVVVV")

s1 < s2                       #=> true
s4.between?(s1, s3)           #=> false
s4.between?(s3, s5)           #=> true
[ s3, s2, s5, s4, s1 ].sort   #=> [Z, YY, XXX, WWWW, VVVVV]

Instance Method Summary collapse

Instance Method Details

#<(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns -1.

Returns:

  • (Boolean)

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# File 'compar.c', line 142

static VALUE
cmp_lt(VALUE x, VALUE y)
{
    VALUE c = rb_funcall(x, cmp, 1, y);

    if (rb_cmpint(c, x, y) < 0) return Qtrue;
    return Qfalse;
}

#<=(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns -1 or 0.

Returns:

  • (Boolean)

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# File 'compar.c', line 159

static VALUE
cmp_le(VALUE x, VALUE y)
{
    VALUE c = rb_funcall(x, cmp, 1, y);

    if (rb_cmpint(c, x, y) <= 0) return Qtrue;
    return Qfalse;
}

#==(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns 0. Also returns true if obj and other are the same object.

Even if obj <=> other raised an exception, the exception is ignored and returns false.

Returns:

  • (Boolean)

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# File 'compar.c', line 89

static VALUE
cmp_equal(VALUE x, VALUE y)
{
    VALUE a[2];

    if (x == y) return Qtrue;

    a[0] = x; a[1] = y;
    return rb_rescue(cmp_eq, (VALUE)a, cmp_failed, 0);
}

#>(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns 1.

Returns:

  • (Boolean)

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# File 'compar.c', line 108

static VALUE
cmp_gt(VALUE x, VALUE y)
{
    VALUE c = rb_funcall(x, cmp, 1, y);

    if (rb_cmpint(c, x, y) > 0) return Qtrue;
    return Qfalse;
}

#>=(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns 0 or 1.

Returns:

  • (Boolean)

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# File 'compar.c', line 125

static VALUE
cmp_ge(VALUE x, VALUE y)
{
    VALUE c = rb_funcall(x, cmp, 1, y);

    if (rb_cmpint(c, x, y) >= 0) return Qtrue;
    return Qfalse;
}

#between?(min, max) ⇒ Boolean

Returns false if obj <=> min is less than zero or if anObject <=> max is greater than zero, true otherwise.

3.between?(1, 5)               #=> true
6.between?(1, 5)               #=> false
'cat'.between?('ant', 'dog')   #=> true
'gnu'.between?('ant', 'dog')   #=> false

Returns:

  • (Boolean)

Returns:

  • (Boolean)

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# File 'compar.c', line 183

static VALUE
cmp_between(VALUE x, VALUE min, VALUE max)
{
    if (RTEST(cmp_lt(x, min))) return Qfalse;
    if (RTEST(cmp_gt(x, max))) return Qfalse;
    return Qtrue;
}