Re^2: Different behaviors between "while" and "map"

Just to expand a little on this: map, grep, foreach and most while constructs all work on perl's concept of lists.

while (<SOME_FILE_HANDLE>)
[download]

is special. it does not act like any other iteration construct, not even like any other while() construct. It explicitly iterates over each record ("line") one by one instead of converting the whole file to a list first.

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Re^3: Different behaviors between "while" and "map" by betterworld (Curate) on Dec 06, 2008 at 01:42 UTC
It helps to know that the loop is expanded to: `while ($_ = <SOME_FILE_HANDLE>){ ... }` [download] This shows that `<...>` is nothing more than a loop condition: the loop body is executed immediately after each evaluation of the `<...>` operator. This is how a while loop works.	[reply] [d/l] [select]
Re^4: Different behaviors between "while" and "map" by JavaFan (Canon) on Dec 06, 2008 at 02:18 UTC
Not for the last 12 years or so. It's expanded to `while (defined ($_ = <SOME_FILE_HANDLE>)) { ... }` [download]	[reply] [d/l]
Re^5: Different behaviors between "while" and "map" by ikegami (Patriarch) on Dec 06, 2008 at 06:09 UTC
Technically, you're both right, because `while ($_ = <SOME_FILE_HANDLE>){ ... }` [download] is expanded to `while (defined ($_ = <SOME_FILE_HANDLE>)) { ... }` [download] But all this is irrelevant. It's not the magical expansion of `<>` that causes the scalar context.	[reply] [d/l] [select]


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