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Re: unexpected result of stringification.

March 19, 2001 13:34
Re: unexpected result of stringification.
Message ID:
Chris Stith <> writes:
>That is so if the examples are taken exactly as is. It is not so if
>the example is put in the context of code following it. From which
>match operator would the next line pull `$1'?
>Nick is talking about a body of code expecting something to be a
>certain way when the code example above is executed. 

No I am not. (The example code is not mine and not a good example.
It has && in it, is calling a builtin as a pseudo-sub and ...)

I am talking about code that uses $1 in general, and with at least 
a basic grasp of how the op tree is built. And with a background
in devious "lexing" schemes. 

Without a lot of flow analysis (that perl does not do) perl cannot tell 
that a particular use of $1 is (always) used in a way that means it should
take a copy, or a way which means it should leave it "lazy".

So my stance is that $1 is lazy, if you want/need a copy then write "$1".

>A line of
>code following the above example shouldn't expect one or the other
>expression to be either `first' or `last', let alone expect which one
>will be the value of `$1'.

Things get less clear when you have something like:

  some_sub( (s/(0x([a-f0-9]+))/another_sub($1)/ie || s/(\d+)/third($1)/e) ?  $1 : ... );

In such cases "lazy" is what _I_ want for that last one at least and only 
by a lot of looking do you know which that is.

>Chris Stith
Nick Ing-Simmons Perl Programming lists via nntp and http.
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