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perlfunc:grep

by gods
on Aug 24, 1999 at 22:42 UTC ( #267=perlfunc: print w/replies, xml ) Need Help??

grep

See the current Perl documentation for grep.

Here is our local, out-dated (pre-5.6) version:


grep - locate elements in a list test true against a given criterion



grep BLOCK LIST

grep EXPR,LIST



This is similar in spirit to, but not the same as, grep(1) and its relatives. In particular, it is not limited to using regular expressions.

Evaluates the BLOCK or EXPR for each element of LIST (locally setting $_ to each element) and returns the list value consisting of those elements for which the expression evaluated to TRUE. In a scalar context, returns the number of times the expression was TRUE.

    @foo = grep(!/^#/, @bar);    # weed out comments

or equivalently,

    @foo = grep {!/^#/} @bar;    # weed out comments

Note that, because $_ is a reference into the list value, it can be used to modify the elements of the array. While this is useful and supported, it can cause bizarre results if the LIST is not a named array. Similarly, grep returns aliases into the original list, much like the way that a for loop's index variable aliases the list elements. That is, modifying an element of a list returned by grep (for example, in a foreach, map() or another grep()) actually modifies the element in the original list.

See also map for an array composed of the results of the BLOCK or EXPR.


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[Corion]: If you cram your slides with that much information, they might work in an "offline" situation but not very well for a live presentation IMO
[ambrus]: Corion: in that case I also ask the people who rent the conference rooms to tell conference organizers about the available tech.
[Corion]: ambrus: No, you're misunderstanding. If you place content too far on the left/right/top/ bottom, people might not see it because the view is obstructed ;)(
[Corion]: In Amsterdam, the screen went down to the bottom of the stage (60cm above ground) and the seating was on the ground, meaning that the rows in the back couldn't see the bottom of slides.
[Corion]: There also were some columns that meant that maybe you couldn't see the left/right edge of a slide.
[ambrus]: Corion: Sure. I've had a course in a 50 seat lecture hall that has two fucking columns in the middle.
[Corion]: Talking about it, the top should be fairly visible in the situations I've experienced at least. The top is uncomfortable for people in the first three rows, but that's life ;)
[ambrus]: The pillars are there because this is in the 6th floor of building R of BME, which is an attic that was built in after the original building, which is also why the elevator doesn't go that high and the windows are tiny.
[Corion]: ambrus: Hehe ;) Yeah - such real life stuff is far more inconveniencing than wasting display area due to screen ratio problems :)
[ambrus]: Corion: yes, it's a bit tricky. you can try to adjust the slides live to cover only a part of the screen, but it's still hard.

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