Update: problem with scalar

sargg55 has asked for the wisdom of the Perl Monks concerning the following question:

Hi monks, I seem to be having a problem with scalar. "Not enough arguments for scalar at a18.pl line 25, near "scalar;" Execution of a18.pl aborted due to compilation errors."

 
#!/usr/bin/perl

use Modern::Perl;
use strict;

system 'clear';

my@array;
my $counter=0;
my $total=0;

open FILE,'testFile.txt';

while (<FILE>) {
    chomp;
    $array[$counter]=$_;
    $total +=$_;
    $counter++
}
close (FILE);


foreach my $scalar(@array)
{
$total+=scalar;
}

printf("\nThe total of the numbers in testfile.txt is %d.\n\n",$total)
+;

my($add,$sub,$div,$mul,$mod)=0;
$add=$array[0] +$array[1];
$sub=$array[0] -$array[3];
$div=$array[5]/$array[1];
$mul=$array[0]*$array[1]*$array[2]*$array[3]*$array[5]*$array[4];
$mod=$array[4]%$array[2];

print "ADD:$add\n";
print "SUB:$sub\n";
print "DIV:$div\n";
print "MUL:$mul\n";
print "MOD:$mod\n";

print ("The answer to 3%5+\(12/4\)-10/5*-3 is".(($array[0] %$array[1])
+ +($array[2]/$array[4])-$array[5]/$array[1]*($array[3]))."\n");

open FILE2,'output.txt';

print FILE2 "ADD:$add\n";
print FILE2 "SUB:$sub\n";
print FILE2 "DIV:$div\n";
print FILE2 "MUL:$mul\n";
print FILE2 "MOD:$mod\n";

print FILE2 ("The answer to 3%5+\(12/4\)-10/5*-3 is".(($array[0]%$arra
+y[1]) + ($array[2]/$array[4])-$array[5]/$array[1]*($array[3]))."\n");

close (FILE2);

print"\nThe Program has terminated. data has been saved to output.txt\
+n\n";
~
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Comment on Update: problem with scalar Download Code

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Re: Update: problem with scalar
by Athanasius (Archbishop) on Apr 24, 2016 at 03:09 UTC

Hello sargg55,

foreach my $scalar(@array) { $total+=scalar; }
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You’ve named the foreach variable $scalar, but in the loop body you’ve left off the $ sigil. Now, it so happens that scalar is a built-in function in Perl (it puts its argument into scalar context), so the interpreter thinks you’re calling the function — without an argument. Add the sigil:

$total += $scalar;
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and it should compile cleanly. See scalar.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^2: Update: problem with scalar

by sargg55 (Novice) on Apr 24, 2016 at 03:14 UTC

Use of uninitialized value in addition (+) at a18.pl line 27.
Use of uninitialized value in addition (+) at a18.pl line 27.
Use of uninitialized value in subtraction (-) at a18.pl line 28.
Use of uninitialized value in subtraction (-) at a18.pl line 28.
Use of uninitialized value in division (/) at a18.pl line 29.
Use of uninitialized value in division (/) at a18.pl line 29.
Illegal division by zero at a18.pl line 29.
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Re^3: Update: problem with scalar

by tangent (Parson) on Apr 24, 2016 at 04:17 UTC

use Data::Dumper;
# ...
# build @array
# ...
print Dumper( \@array );
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Re^3: Update: problem with scalar

by Laurent_R (Canon) on Apr 24, 2016 at 07:44 UTC

@array

testFile.txt

Perhaps you could change the file opening line as follows:

open FILE, "<", 'testFile.txt' or die "Cannot open testFile.txt $!";
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BTW, you should always check whether such OS related statements succeed.

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Re: Update: problem with scalar
by Athanasius (Archbishop) on Apr 24, 2016 at 08:42 UTC

Another problem is that you open the output file like this:

open FILE2,'output.txt';
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But with no mode specified, this defaults to reading (i.e., input mode), so each attempt to print to the file results in an error message like this:

print() on closed filehandle FILE2 at ...
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As a general rule, you should prefer the three-argument form of open with the mode made explicit:

open FILE,  '<', 'testFile.txt';
...
open FILE2, '>', 'output.txt';
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And, as Laurent_R says, you should always check whether the open call succeeds. If you don’t want to write ... or die ... after each call, you can simply add the pragma:

use autodie;
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at the head of your script. See autodie.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re: Problem when opening a file with perl
by stevieb (Canon) on Apr 23, 2016 at 23:29 UTC

Welcome to the Monastery, sarg55!

Please show the code you're using and having trouble with. Place the code within <code></code> tags.

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Re: Update: problem with scalar
by graff (Chancellor) on Apr 24, 2016 at 19:33 UTC

use Scalar::Util 'looks_like_number';

my @array;
while (<>) {
    chomp;
    if ( looks_like_number( $_ )) {
        push @array, $_;
    }
    else {  # skip this part if you don't care to know about bad input
+...
        warn "Unusable input line skipped: $_\n";
    }
}
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UPDATE: Having played with that snippet a bit, I'm happy to notice that leading and trailing whitespace characters do not affect the results of "looks_like_number()" (i.e. it returns true for " 123 ", "\t-456\n", and so on). The same is true for arithmetic operators: you can add, subtract, multiply and divide numeric strings that have leading and trailing whitespace.

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