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Regexmatches oddity noted
Posted: 26 Apr 2017 01:01
by Papoulka
It's convenient that variables will often concatenate automatically with other symbols, especially in regex use. For one thing it makes the code much more readable. But I understand that this may not be a "guaranteed" behavior.
So ONLY in the interest of pointing out what MAY be unintended operation:
Code: Select all
/*
$tokn="X";
$targ="_X_";
echo regexmatches($targ, $tokn);
echo regexmatches($targ, _$tokn);
echo regexmatches($targ, $tokn_);
The point is that a leading "_" will concatenate OK for the regex, but a trailing underscore will not. In contrast, a trailing "\." does work. I can work around the issue with intermediate variables or full concatenation syntax. So just noting this.
Re: Regexmatches oddity noted
Posted: 26 Apr 2017 05:55
by highend
It happens because XY is very (imho: too) tolerate on how strings can be used
XY interprets the "_" as a string. You should double quote + concatenate it to make this clear (or double quote both together)
E.g.:
This isn't interpreted as a string but a variable name!
Use
to get the correct result
Help file, Advanced Topics - Scripting - Variables - Format and Scope
Re: Regexmatches oddity noted
Posted: 26 Apr 2017 10:57
by PeterH
A bit further:
_$tokn in general is a syntax error (string "_" outside quotes) - but tolerated by XY.
But is reported when syntax check is on (ScriptStrictSyntax=1).
"_$tokn" is a variable prefixed by "_", while
"$tokn_" is the variable $tokn_
For me the first is a problem - the others are useful results of correct interpretation of syntax.
Re: Regexmatches oddity noted
Posted: 26 Apr 2017 17:17
by Papoulka
Thanks for the detailed replies, which explain things very clearly. I had forgotten the variable definition rules while buried in regex issues, and assumed this might be related to the latter.
Short-cut concatenation is very convenient but risky. I'll remember at least that much, going forward.