Literal Source Parameters At Runtime

tomazos has asked for the wisdom of the Perl Monks concerning the following question:

I want to take the literal source code of the parameter of a function call, and use it as a string at runtime. (...in a similiar fashion to the # operator in the context of a macro definition in the C/C++ preprocessor.)

sub literalize
{
    ????
}

sub assert($)
{
    my ($condition) = @_;

    my $literal_condition_code = literalize(@_);

    if ($condition)
    {
       print "assertion failed: $literal_condition_code\n";
    }
}

assert(42 == 24);
[download]

Output:

assertion failed: 42 == 24
[download]

The C/C++ code would be:

#define assert(condition) { if (!condition) { printf("assertion failed
+: %s\n", #condition); } }
[download]

Anyone know how to do something like this in Perl?

Thanks,
Andrew.

Comment on Literal Source Parameters At Runtime Select or Download Code

Replies are listed 'Best First'.
Re: Literal Source Parameters At Runtime by BrowserUk (Patriarch) on Oct 29, 2007 at 05:10 UTC
Take a look at Smart::Comments `c:\>perl -MSmart::Comments -lw ### assert: 42 == 42 ### assert: 42 == 43 ^Z ### 42 == 43 was not true at - line 2. c:\>perl -MSmart::Comments -lw ### assert: 42 == 42 my $var = 43; ### assert: $var == 42 ^Z ### $var == 42 was not true at - line 3. ### $var was: 43` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l]
Re: Literal Source Parameters At Runtime by tuxz0r (Pilgrim) on Oct 29, 2007 at 15:37 UTC
`perl` also has the -P option , which passes the program through the C preprocessor before exectution. So, using that option, you could use the exact same approach as you are in C++, using a `#define`. `#! /usr/bin/perl -P use strict; #define assert(exp) { if (!(exp)) { printf("assertion failed %s\n", #e +xp); } } my $var = 30; assert($var == 32); exit 0;` [download] Output: `assertion failed 30 == 32` [download] --- echo S 1 [ Y V U \| perl -ane 'print reverse map { $_ = chr(ord($_)-1) } @F;'	[reply] [d/l] [select]


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