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Comment by chao- | Hacker News Reader

#if and #ifTrue are yours if you want them:

  class TrueClass
    def if = true
    def ifTrue = true
  end

  class FalseClass
    def if = false
    def ifTrue = false
  end

  true.if
  # => true
  false.if
  # => false

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In Smalltalk those methods don't return `true`. They take a block and evaluate it if the boolean receiving the message

    (a > b) ifTrue: [ "do something" ]

EDIT: to clarify what's happening there, `>` is a message sent to `a` that will result in a boolean. The True class and False class both understand the ifTrue: message and `True>>ifTrue:` executes the block whereas `False>>ifTrue:` just throws it away.

There's no `if` keyword in the language. Control flow is done purely through polymorphism.

I apologize for my lack of Smalltalk knowledge. As you can imagine, you can do similar in Ruby by defining ifTrue to accept a block, even adding ifTrue on other all objects and defining something similar:

  class TrueClass
    def ifTrue(&block) = block.call
  end

  class FalseClass
    def ifTrue(&block) = nil
  end

  class Object
    def ifTrue(&block) = block.call
  end
      
  class NilClass
    def ifTrue(&block) = nil
  end

If ck45's core complaint was that this is not baked into the language, I will agree that it is less convenient for lack of a default.

Certainly possible: add ifTrue as a method to TrueClass and FalseClass.

It just isn't very fast.

problem is not with ifTrue, and not with it's performance, it's easy to do. it is "ifTrue:ifFalse:"

also it is common to do assignments in the "if", and with actual method and blocks scope of the introduced variable would be different and everyone would be tripping on it all the time.

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