[LON-CAPA-users] another regular expression

[H. K. Ng]

Hi,

I am trying to construct some general regular expressions and ran into this 
problem.

$coeff = &random(1,5);
$c_re = '\Q'.$coeff.'\E'.($coeff == 1 ? '?' : '');
$var = '\Qx\E';

$re = '/^\s*$c_re\s*\*?\s*$var\s*$/';

will not work even though it shows as answer

$re = '/^\s*\Q1\E?\s*\*?\s*\Qx\E\s*$/';

when $coeff = 1.

If however, the regular expression is constructed as

$re = '/^\s*\Q$coeff\E'.($coeff == 1 ? '?' : '').'\s*\*?\s*\Qx\E\s*$/';

it works fine. What puzzles me is that the answers displayed for both are 
identical. Any ideas?

-hk