[ruby-talk:11649] Re: assert() library in Ruby?

Eric Sven Ristad <[e-mail]> writes:

> How can I achieve the effect of the assert() macro from C in Ruby?
> In particular,
> 
> 1. assert(<expr>) will print something like
> 
> 	"Assertion failed: <expr>, file <file>, line <line>"
> 
>    only when <expr> evaluates to false, where <file> and <line> refer
>    to the location of the assert() call rather than the location of
>    the assert() definition
> 
> 2. all asserts are ignored if !$DEBUG, ie.,
>    assert(<expr>) does not even evaluate <expr> when !$DEBUG

  DEBUG = false  # or true

  def assert
    if DEBUG
      result = yield
      raise "Assertion failed" if !result
    end
  end

  assert { 1 == 1 }

  assert { 1 == 2 }

This defers the evaluation of the code in the block until the method
'assert' can determine if DEBUG is set to true.

It doesn't print the expression itself, but it does give you a full
backtrace. Also, as it's an exception, you can catch it if you want.


Regards


Dave