> Bryan R Harris wrote:
>>
>>>> returns "true" or "false" (1 or '') and in list context it returns the
>>>> contents of any capturing parentheses in the pattern.
>>>>
>>>> The expression:
>>>>
>>>> ( $ptypeline =~ /movable.+(sine|geo|radial|ortho)/i
>>>> )[ 0 ]
>>>>
>>>> is a list slice so the regular expression is in list context but the slice
>>>> is
>>>> a single value so the expression is a scalar.
>>>>
>>>> The || operator will only work with scalar values, not with lists, so this
>>>> works because the list has been converted to a scalar with the list slice.
>>>>
>>>> John
>>> ********************************************
>>> the list context represents everything between the / /
>>> and the slice context represents [ 0 ] which is
>>> assigned as a scalar to $ptypeline.
>>>
>>> Correct?
>>
>>
>> Any time you surround something with parenthesis () it is considered "list
>> context", i.e.
>>
>> Scalar context: $a = $ptypeline =~ /movable.+(sine|geo|radial|ortho)/i;
>>
>> In scalar context, perl is trying to assign a scalar to $a. In scalar
>> context that expression returns a 1 or 0 depending on whether it was able to
>> find that regular expression inside of $ptypeline. (Or if I had a /gi at
>> the end it would return the number of matches it found).
>>
>> List context: @a = ($ptypeline =~ /movable.+(sine|geo|radial|ortho)/i);
>>
>> This is list context, meaning that perl is trying to get a list out of that
>> expression. In list context, that expression returns whatever items it
>> found in sets of parenthesis -- in this case, if ptypeline had "ortho", @a
>> would be ("ortho").
>
> No. It is list context because "@a =" forces list context. In other words:
>
> @a = ( $ptypeline =~ /movable.+(sine|geo|radial|ortho)/i );
>
> and:
>
> @a = $ptypeline =~ /movable.+(sine|geo|radial|ortho)/i;
>
> are both in list context, the parentheses are superfluous. However in:
>
> $a = $ptypeline =~ /movable.+(sine|geo|radial|ortho)/i;
>
> the expression is in scalar context because "$a =" forces scalar context.
> Even if you add parentheses:
>
> $a = ( $ptypeline =~ /movable.+(sine|geo|radial|ortho)/i );
>
> it is still in scalar context, while:
>
> ( $a ) = $ptypeline =~ /movable.+(sine|geo|radial|ortho)/i;
>
> is in list context because $a is now part of a list.
Umm... So would this do what I want also?
($ptype)=($projection =~ /movable.+(sine|geo|radial|ortho)/i)
or $ptype="(missing)";
It seems to...
- B
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