On Thu, 2002-04-04 at 15:01, Bruce Ambraal wrote:
> Hi all
>
> My code below does the following :
> - Reads from STDIN
> - Splits the input on whitespace
> - And prints the frequency of terms, with each term printed next to its frequency on
>STDOUT.
>
> I need another approach (code) to do the same things
>
>
<snip />
What sort of approach? This seems to be the optimal (I would even say
canonical) solution to the find-the-frequency-of-words-in-a-stream
problem.
> if( exists $freq{$w} ){
> $freq{$w}++;
> }else{
> $freq{$w} = 1;
> }
<snip />
This if is not necessary. The '++' operator does not complain about the
presence of undef (it just treats it like 0) and hash have
autovivification (the spring into life when you use them). So you can
say
$freq{$w}++;
here instead.
The only other simple solution is the same algorithm with less code:
<example>
#!/usr/bin/perl -lan
$freq{$_}++ for @F;
END { print "$_ occured $freq{$_} times" for keys %freq }
</example>
-n
causes Perl to assume the following loop around your
program, which makes it iterate over filename argu
ments somewhat like sed -n or awk:
LINE:
while (<>) {
... # your program goes here
}
-l[octnum]
enables automatic line-ending processing. It has two
separate effects. First, it automatically chomps
"$/" (the input record separator) when used with -n
or -p. Second, it assigns "$\" (the output record
separator) to have the value of octnum so that any
print statements will have that separator added back
on. If octnum is omitted, sets "$\" to the current
value of "$/".
-a
turns on autosplit mode when used with a -n or -p.
An implicit split command to the @F array is done as
the first thing inside the implicit while loop pro
duced by the -n or -p
The only other trick here is the use of the END block to that is
executed at the end of the program (after the last normal statement is
reached or the program exits due to a return or exit).
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