Re^2: Insert row from file

At last I more or less understand it --but you mentioned in first line comment "(keyed on 2nd line)" --how is this done -the file was read in and every 2nd line is the key --is this some sort of default-what if I wanted every odd line (lines 1,3,5 etc) to be the keys??
Thanx
Smbs

Comment on Re^2: Insert row from file

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Re^3: Insert row from file by Gilimanjaro (Hermit) on Feb 04, 2005 at 11:16 UTC
It works because of the way the while loop works: The conditional in the while loop always gets evaluated first, before the content of the loop block. The <A> operator, when used in a while conditional, assigns the line gotten from file A to $_, starting with the 1st line. The body of the loop, again uses the <A> operator, which gets the next line; you can access a line only once using the <> operator. I use it directly as the key to the %pairs hash, so the key is the 2nd line. It assigns the value of $_ (which was set in the while conditional) to this element of %pairs. The loop evaluates the conditional again, gets the 3rd line, and assigns it to $_, and the body does the same all over again with the fourth line. So the even/odd mechanism is caused by the double use of <A>. If I wanted to key on the odd lines, I'd've used `$pairs{$_}=<A>;`	[reply] [d/l]

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Re^3: Insert row from file
by Gilimanjaro (Hermit) on Feb 04, 2005 at 11:16 UTC

It works because of the way the while loop works: The conditional in the while loop always gets evaluated first, before the content of the loop block. The <A> operator, when used in a while conditional, assigns the line gotten from file A to $_, starting with the 1st line.

The body of the loop, again uses the <A> operator, which gets the next line; you can access a line only once using the <> operator. I use it directly as the key to the %pairs hash, so the key is the 2nd line. It assigns the value of $_ (which was set in the while conditional) to this element of %pairs.

The loop evaluates the conditional again, gets the 3rd line, and assigns it to $_, and the body does the same all over again with the fourth line. So the even/odd mechanism is caused by the double use of <A>.

If I wanted to key on the odd lines, I'd've used $pairs{$_}=<A>;

[reply]
[d/l]