Re^2: array splitting

in reply to Re: array splitting
in thread array splitting

I note the code I posted actually didn't even work for the first list. I note this code does work and there's a few things in this that I don't know well, so good for learning, thank you.
if (! @times) presumably means if there is nothing in the array? This is a general confusion I have with perl, about what tests for a value being present in a variable and what "undef" means. I assume the exclamation mark I can always use to determine if values are (not) present in a variable from now on? Colin

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Re^3: array splitting by blazar (Canon) on Jun 05, 2007 at 18:09 UTC
if (! @times) presumably means if there is nothing in the array? Yes. Alternatively you could use `unless (@times) { # ...` [download] which may be clearer to understand naively, based on the rationale that a full thingy is true and an empty one is false. This is a general confusion I have with perl, about what tests for a value being present in a variable and what "undef" means. undef is a builtin function which can take a variable and give it a special value which is also its own return value. The latter is thus in turn also called `undef`: in fact the function is often used with no argument in which case it simply returns it. undef is a particular false value, precisely the one that also have variables which have not been initialized at all. I assume the exclamation mark I can always use to determine if values are (not) present in a variable from now on? The exclamation mark is simply a logical "not" that turns a true value into a false one and vice versa.	[reply] [d/l] [select]

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Re^3: array splitting
by blazar (Canon) on Jun 05, 2007 at 18:09 UTC

if (! @times) presumably means if there is nothing in the array?

Yes. Alternatively you could use

unless (@times) {  # ...
[download]

which may be clearer to understand naively, based on the rationale that a full thingy is true and an empty one is false.

This is a general confusion I have with perl, about what tests for a value being present in a variable and what "undef" means.

undef is a builtin function which can take a variable and give it a special value which is also its own return value. The latter is thus in turn also called undef: in fact the function is often used with no argument in which case it simply returns it. undef is a particular false value, precisely the one that also have variables which have not been initialized at all.

I assume the exclamation mark I can always use to determine if values are (not) present in a variable from now on?

The exclamation mark is simply a logical "not" that turns a true value into a false one and vice versa.

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