How to get the max value from an array in Perl? - perl

Question

I have an input source as follows. What I want to do is capture the numeric value on each of the Layer lines into an array and then print out the maximum value.
input
MACRO cell_1
size 0.1 by 0.1 ;
pin a
(....same topology as pin vcc)
END a
pin b
(.....same topology as pin vcc)
END b
Pin vcc
aaaa
bbbb
Port
Layer m2 ;
END
CCC
DDD
Port
Layer m1 ;
END
EEE
FFF
Port
Layer m0 ;
END
END vcc
pin d
(....same topology as pin vcc)
END d
END cell_1
MACRO cell_2
(repeated)
END cell_2
my code:
foreach my $file ( #files ) { # #files = multiple path of abc/def/fgh/cell_lef
open( INFILE, "<$file" ) || die "Can not open stdcell_file\n";
my #lines = <INFILE>;
close INFILE;
$init = 1;
$delimiter =~ /^$/; # between each MACRO. haven't utilize this yet
foreach (#lines) {
if ( $init ) {
$path = 1;
$init = 0;
#num = ();
}
if ( $path ) {
if ( /MACRO\s+(\S+) /) {
$cellname = $1; print "$cellname\n";
}
if ( /SIZE\s+(\S+)\s+(\S+)\s+(\S+)/ ) {
$footprint_x = $1;
$footprint_y = $3;
print "$footprint_x $footprint_y\n";
}
if ( /PIN vcc/ .. /END vcc/ ) {
#grab the highest value from layer (m*)
#print "max layer = m*"
}
$init = 1;
}
}
}
intended output
cell_1
0.1 0.1
m2
cell_2
0.2 0.2
m3
The code I am attempting to use:
if ( /PIN vcc/../END vcc/ ) {
if ( /LAYER\s+m(\S+) / ) {
push(#num, $1);
print "#num";
}
}
The problem with my code so far is that when I print the value of #num, all the values are joined together as a string (210) instead of individual elements: 2 1 0 — so I am not able to do the sorting to get the max value.
Update: I am not sure how to integrate the while into my code as I'm using foreach as my main loop

Answer 1

Your code is capturing the numbers ok, it's just that you're printing the whole array. Perl's default separator for array elements when you print an array is "" ie, nothing - so, it looks like a single string but it's three (or however many) elements printed next to each other without a separator.
You can iterate over input line by line in Unix filter style with while (<>) {. You can switch on a "scanning mode" flag when "PIN vcc" is found and switch it off when "END vcc" is found. After that, use a regex to search for the layer line but always use 'extended mode' /x so you can use whitespace in your regex.
As the regex's for switching modes and capturing the layer number are mutually exclusive, you can let the other checks happen after a check succeeds - just be aware that if future changes result in overlapping cases, you need to do a next when one of the regex succeeds.
Finally, List::Util is a core module so, you might as well grab the max function from it;
use v5.12;
use warnings;
use List::Util qw( max );
my #num ;
my $scanning = 0;
while (<>) {
$scanning = 1 if /PIN vcc/ ;
$scanning = 0 if /END vcc/ ;
next unless $scanning ;
push #num, $1 if /Layer \s+ m (\d+) /x ;
}
say "Max layer number found: ", max(#num) ;

Answer 2

Or simply use sort function for to do it.
my #values ;
while (<DATA>)
{
push (#values , $1) if (/Layer\s+m(\d+)\s;/);
}
my ($max) = sort{$b <=> $a} #values ;
print "$max\n";
__DATA__
Pin vcc
aaaa
bbbb
Port
Layer m3 ;
END
CCC
DDD
Port
Layer m1 ;
END
EEE
FFF
Port
Layer m0 ;
END
use sort function and store the first result into list contain the variable $max.

Answer 3

my #data = <DATA> ;
my #num ;
foreach (#data) {
push #num, $1 if /Layer\s+m(\S+)/ ;
}
# home made max() - sorts an anonymous array and prints the last element
print [ sort { $a <=> $b } #num ]->[-1] , "\n" ;
__DATA__
Pin vcc
aaaa
bbbb
Port
Layer m2 ;
END
CCC
DDD
Port
Layer m1 ;
END
EEE
FFF
Port
Layer m0 ;
END
END vcc

Answer 4

Using map to fetch numbers from file. sort the number and get maximum number.
#!/usr/bin/perl
use strict;
use warnings;
my $max = (sort{$b <=> $a }map{/Layer\s+m(\d+)/} <DATA>)[0];
print $max,"\n";
__DATA__
Pin vcc
aaaa
bbbb
Port
Layer m3 ;
END
CCC
DDD
Port
Layer m1 ;
END
EEE
FFF
Port
Layer m0 ;
END

Answer 5

First, you don't need to store all values if you're looking only for max value; and second, print the max value after the loop is over,
my $max = "-inf";
if (/PIN vcc/ .. /END vcc/) {
$max = $1 if /LAYER\s+m(\S+)/ and $max < $1;
}
# ..
print $max, "\n";