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Re: Minor querry!!
by plaid (Chaplain) on Jun 24, 2000 at 00:40 UTC
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You probably want something like:
if($a =~ /\D/) {
# Not a number
}
The /D matches non-digits, so this will be true if $a
contains any non-digits. | [reply]
[d/l] |
Re: Minor querry!!
by Shendal (Hermit) on Jun 24, 2000 at 00:40 UTC
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I think you want something like this:
use strict;
use warnings;
my($a) = <STDIN>;
chomp($a);
if ($a !~ /^\d+$/) {
print "Sorry - you didn't give me a number.\n";
exit 1;
} else {
print "Yay! That's a number!\n";
}
Hope that helps,
Shendal | [reply]
[d/l] |
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Another variation on Shendal's solution could be to allow
for decimals. I hardly ever work with whole numbers (not through
choice, but because of the data we are responsible for here).
my $number = <STDIN>;
chomp $number;
if ($number !~ /^\d+\.?\d*$/) {
print "$number is not a number.\n";
exit 1;
} else {
print "$number is a number!\n";
}
I hope this proves useful to someone.
mrmick | [reply]
[d/l] |
RE: Minor querry!!
by sean (Beadle) on Jun 24, 2000 at 04:51 UTC
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if ($a eq $a+0) {
#$a is a decimal number
}
This won't work if you were planning on accepting input numbers in hex or octal though, only decimal. | [reply]
[d/l] |
Re: Minor querry!!
by Adam (Vicar) on Jun 24, 2000 at 00:40 UTC
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if( $input =~ /^(\d+)$/ )
{
$a = $1;
}
else
{
print "Please enter a number\n"
}
or something like that. | [reply]
[d/l] |
Re: Minor query
by spudzeppelin (Pilgrim) on Jun 24, 2000 at 01:00 UTC
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Or, supposing you want to allow decimals:
FOO: $a = <STDIN>;
chomp($a);
$a =~ tr/0-9.//cd;
if (length($a) < 1) { print "Please enter a number\n"; goto FOO; }
Spud Zeppelin * spud@spudzeppelin.com | [reply]
[d/l] |
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While your example using tr/// is interesting, the use of the g-word (goto) is a bad idea. Instead, use a loop:
while (!$stop) {
$a = <STDIN>;
chomp($a);
$a =~ tr/0-9.//cd;
if (length($a) < 1) {
print "Please enter a number\n";
$stop = 1;
}
}
Of course, I think the other examples, especially plaid's suggestion are less obfuscated.
| [reply]
[d/l] |
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a slightly nicer fusion of your two methods is the following:
PROMPT: {
chomp($a = <STDIN>);
$a =~ tr/0-9.//cd;
unless (length($a))
{
print "Please enter a number\n";
redo PROMPT;
}
}
| [reply]
[d/l] |
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{
print "Number?\n";
redo unless <STDIN> =~ /^\d+$/;
}
Or, to save the value (which can be useful :)
{
print "Number?\n";
redo unless <STDIN> =~ /^(\d+)$/ and $number=$1;
}
But my personal favorite would be simply:
print "Number?\n" while <STDIN> !~ /^\d+$/;
| [reply]
[d/l]
[select] |
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I beg to differ. "Never, never, never use goto!" is one
of those programming mantras which are taught to beginners
because at that level, the temptation is to use it where it
is not appropriate. However, as a developer becomes more
experienced, the usefulness, clarity, and simplicity of an
unencumbered "jump over there" instruction make it more
valuable when used sparingly and appropriately. And in this
case, an exception handler of a sort that basically says "go
back three lines and try it again," the use is very appropriate.
While we are drifing dangerously offtopic, I am going to ask you
to reconsider the two snippets above, and tell me which is actually
more readable -- the one that obfuscates a goto with a while loop, or
the one that explicity uses the goto when the goto is EXACTLY the
instruction being used in both, algorithmically.
Spud Zeppelin * spud@spudzeppelin.com
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