From: "Paul E. Black" <p.black@...>
Date: 2008-01-30T03:06:51+09:00
Subject: Re: assert{ 2.0 } - a new kind of assertion

On Tuesday 29 January 2008 10:29, Phlip wrote:
> I have invented a new concept of developer test assertions. This post is a
> preview of its features, before I release it for Ruby. Porting it to other
> languages is left as an exercise for the reader.
> 
>    assert{ 2.0 }
> 
> I don't like the simple assertions - assert_equal, assert_match,
> assert_not_nil, etc, in my developer tests. They only exist for
> one reason - to print out their values when they fail. And then
> they don't even reflect their variable names, either.
> 
> So I wrote an assertion to replace them. Put whatever you want
> into it; it prints out your expression, and all its values.
> Essentially like this:
> 
>    x = 43
>    assert{ x == 42 } --> x == 42
>                              x --> 43
> 
>    deny{ x == 43 }   --> x == 43 should not pass
>                              x --> 43

Phlip,

Very nice!  I've used C's macro pre-processor to do something like
that for some 20 years.

#ifdef RIGOROUS
#define ASSERT(ex) {if(!(ex))fprintf(stderr,"ex false in %s, line %d\n",__FILE__,__LINE__);}
#else
#define ASSERT(ex)
#endif

The default is NOT to check the assertion, since some take quite a bit
of time.  Here are some examples:
    ASSERT(-4712 <= year && year != 0)
    ASSERT(!(year == 1582 && month == 10 && 4 < day && day < 15))
    ASSERT(0 <= newStream->queueNextEmpty && newStream->queueNextEmpty < newStream->queueSize)
       ASSERT(streamp->queue[at - size])
    ASSERT(filename && *filename)
    ASSERT(compare(e1, e2) == result);
    ASSERT(0 <= linebufp-linebuf && linebufp-linebuf <= line_width)

Here's comes from the last one when the assertion fails

0 <= linebufp-linebuf && linebufp-linebuf <= line_width false in format.c, line 110

-paul-