Safe Bool Type - `Bool()`, `to_b`, `to_bool`, and More

safebool gem / library - safe bool / boolean type adds Bool(), to_b, parse_bool / to_bool, bool?, false?, true?, true.is_a?(Bool)==true, false.is_a?(Bool)==true, and more

home :: github.com/s6ruby/safebool
bugs :: github.com/s6ruby/safebool/issues
gem :: rubygems.org/gems/safebool
rdoc :: rubydoc.info/gems/safebool

Why `Bool` in Ruby?

false.class           #=> FalseClass
true.class            #=> TrueClass
false.is_a?(Bool)     #=> NameError: uninitialized constant Bool
true.is_a?(Bool)      #=> NameError: uninitialized constant Bool
true.class.ancestors  #=> [TrueClass, Object, Kernel, BasicObject]
false.class.ancestors #=> [FalseClass, Object, Kernel, BasicObject]

# -or-

false.to_s            #=> "false"
true.to_s             #=> "true"
false.to_i            #=> NoMethodError: undefined method `to_i' for false:FalseClass
true.to_i             #=> NoMethodError: undefined method `to_i' for true:TrueClass
Integer(false)        #=> TypeError: can't convert false into Integer
Integer(true)         #=> TypeError: can't convert true into Integer

# -or-

"false".to_b          #=> NoMethodError: undefined method `to_b' for String
0.to_b                #=> NoMethodError: undefined method `to_b' for Integer
Bool("false")         #=> NoMethodError: undefined method `Bool' for Kernel
Bool(0)               #=> NoMethodError: undefined method `Bool' for Kernel

"true".to_b           #=> NoMethodError: undefined method `to_b' for String
1.to_b                #=> NoMethodError: undefined method `to_b' for Integer
Bool("true")          #=> NoMethodError: undefined method `Bool' for Kernel
Bool(1)               #=> NoMethodError: undefined method `Bool' for Kernel

...

Everything is true except false and nil. Just use the bang bang (!!) doubled-up (logical) boolean not operator for to_b conversion:

!! false   #=> false
!! nil     #=> false

!! true    #=> true
!! "false" #=> true
!! ""      #=> true
!! 0       #=> true
!! 1       #=> true
!! []      #=> true
!! {}      #=> true
!! 0.0     #=> true
!! :false  #=> true
# ...

Why? Why not? Discuss.

Intro

What's a Bool?

In computer science, the Boolean data type is a data type that has one of two possible values (usually denoted true and false), intended to represent the two truth values of logic and Boolean algebra. It is named after George Boole, who first defined an algebraic system of logic in the mid 19th century.

(Source: Boolean data type @ Wikipedia)

Trivia Quiz - The States of Bool

Q: How many states has a boolean type in a (classic) programming language?

[ A ] 1 - One State
[ B ] 2 - Two States
[ C ] 3 - Three States
[ D ] Other. Please tell

A: In practice¹ three really :-), that is, true, false and undefined (e.g. nil).

1: with nil-able / null-able types

Usage

String • Symbol • Integer • Kernel

false.is_a?(Bool)     #=> true
true.is_a?(Bool)      #=> true
true.class.ancestors  #=> [TrueClass, Bool, Object, Kernel, BasicObject]
false.class.ancestors #=> [FalseClass, Bool, Object, Kernel, BasicObject]

# -or-

false.to_i            #=> 0
true.to_i             #=> 1

# -or-

"false".to_b          #=> false
0.to_b                #=> false
Bool("false")         #=> false
Bool(0)               #=> false

"true".to_b           #=> true
1.to_b                #=> true
Bool("true")          #=> true
Bool(1)               #=> true

How about handling errors on invalid bool values when converting / parsing?

to_b always returns a bool even if the conversion / parsing fails e.g. true for invalid numbers or strings and false (for empty / blank strings) on error
parse_bool / to_bool always returns nil if the conversion / parsing fails
Bool() always raises an ArgumentError if the conversion / parsing fails and a TypeError if the conversion is unsupported (e.g. expected required parse_bool method missing / undefined)

"2".to_b                #=> true
"2".to_bool             #=> nil
"2".to_bool.bool?       #=> false
"2".to_bool.is_a?(Bool) #=> false
Bool("2")               #=> ArgumentError: invalid value "2":String for Bool(); parse_bool failed (returns nil)

2.to_b                  #=> true
2.to_bool               #=> nil
2.to_bool.bool?         #=> false
2.to_bool.is_a?(Bool)   #=> false
Bool(2)                 #=> ArgumentError: invalid value 2:Integer for Bool(); parse_bool failed (returns nil)

"".to_b                  #=> false
"".to_bool               #=> nil
"".to_bool.bool?         #=> false
"".to_bool.is_a?(Bool)   #=> false
Bool("")                 #=> ArgumentError: invalid value "":String for Bool(); parse_bool failed (returns nil)

# note: same for "blank" strings
"  ".to_b                #=> false
"  ".to_bool             #=> nil

...

String

Returns true if string is one of these values: t, true, on, y, yes, 1.
Returns false if string is one of these values: f, false, off, n, no, 0.

For invalid boolean string values to_b returns true by default except for empty / blank strings where to_b returns false. See the "Handling Errors" section for more options.

Note: The Bool.parse method ignores leading and trailing spaces and upper and lower cases e.g. FaLSe is the same as false.

'1'.to_b        #=> true
't'.to_b        #=> true
'T'.to_b        #=> true
'true'.to_b     #=> true
'TRUE'.to_b     #=> true
'on'.to_b       #=> true
'ON'.to_b       #=> true
'y'.to_b        #=> true
'yes'.to_b      #=> true
'YES'.to_b      #=> true

' 1 '.to_b      #=> true
' t '.to_b      #=> true
' T '.to_b      #=> true
' true '.to_b   #=> true
' TRUE '.to_b   #=> true
' on '.to_b     #=> true
' ON '.to_b     #=> true
' y '.to_b      #=> true
'Y'.to_b        #=> true
' Y '.to_b      #=> true
' yes '.to_b    #=> true
' YES '.to_b    #=> true

'0'.to_b        #=> false
'f'.to_b        #=> false
'F'.to_b        #=> false
'false'.to_b    #=> false
'FALSE'.to_b    #=> false
'off'.to_b      #=> false
'OFF'.to_b      #=> false
'n'.to_b        #=> false
'N'.to_b        #=> false
'no'.to_b       #=> false
'NO'.to_b       #=> false

' 0 '.to_b      #=> false
' f '.to_b      #=> false
' F '.to_b      #=> false
' false '.to_b  #=> false
' FALSE '.to_b  #=> false
' off '.to_b    #=> false
' OFF '.to_b    #=> false
' n '.to_b      #=> false
' N '.to_b      #=> false
' no '.to_b     #=> false
' NO '.to_b     #=> false

''.to_b         #=> false
' '.to_b        #=> false

'xxx'.to_b      #=> true
'bool'.to_b     #=> true

''.to_bool      #=> nil
' '.to_bool     #=> nil
'xxx'.to_bool   #=> nil
'bool'.to_bool  #=> nil

Symbol

Same as self.to_s.to_b or self.to_s.to_bool.

:'1'.to_b      #=> true
:t.to_b        #=> true
:true.to_b     #=> true
:on.to_b       #=> true
:y.to_b        #=> true
:yes.to_b      #=> true

:'0'.to_b      #=> false
:f.to_b        #=> false
:false.to_b    #=> false
:off.to_b      #=> false
:n.to_b        #=> false
:no.to_b       #=> false

:xxx.to_b      #=> true
:bool.to_b     #=> true

:xxx.to_bool   #=> nil
:bool.to_bool  #=> nil

Integer

Returns false if the number is zero and true otherwise.

0.to_b      #=> false
1.to_b      #=> true
2.to_b      #=> true
-1.to_b     #=> true
-2.to_b     #=> true

0.to_bool   #=> false
1.to_bool   #=> true

2.to_bool   #=> nil
-1.to_bool  #=> nil
-2.to_bool  #=> nil

Kernel

More methods added to Kernel include bool?, false?, true?. Example:

# bool? - returns true if object class is TrueClass or FalseClass, otherwise false

true.bool?    #=> true
false.bool?   #=> true
nil.bool?     #=> false

# false? - returns true if object class is FalseClass, otherwise false

false.false?  #=> true
true.false?   #=> false
nil.false?    #=> false

# true? - returns true if object class is TrueClass, otherwise false

true.true?    #=> true
false.true?   #=> false
nil.true?     #=> false

And some more. See the safebool.rb source.

License

The safebool scripts are dedicated to the public domain. Use it as you please with no restrictions whatsoever.

Questions? Comments?

Send them along to the wwwmake forum. Thanks!

Safe Bool Type - Bool(), to_b, to_bool, and More

Why Bool in Ruby?