Variable contents numeric or string?

[dozier]

What's the best way to test if a scalar contains a string or number?

 

[PaulTEG]

use a regex to see if its a number, and if it isn't, it must be a string ??
--Paul

It's important in life to always strike a happy medium, so if you see someone with a crystal ball, and a smile on their face ...

 

[BrianAtWork]

A specific example of a regex to accomplish this would be shown in the following code:

$test = "12a34";
if ($test =~/^\d+$/) {
  print "This is a number!\n";
}
else {
  print "This is not a number!\n";
}

This will check the string $test to see if it is a number (1 or more numbers).
If you wanted to check if the string had zero numbers in it, you can try this.

$test = "12a34";
if ($test =~/^[^\d]+$/) {
  print "This string contains no numbers!\n";
}
else {
  print "This string contains numbers!\n";
}

Also - if you want to check specifically for words in the variable (an not just check if it has numbers or not), you can use this:

$test = "12a34";
if ($test =~/^[a-zA-Z_]+$/) {
  print "This string contains only letters!\n";
}
else {
  print "This string does not contains only letters!\n";
}

You can test each example, and change $test to contain any combination of letters or numbers...

Hope this helps!

 

[dozier]

Thank you both. I thought about using regexps right after I clicked submit, but decided not to respond again in order to see if anyone had any other ideas. I implemented the regexp solution and it works, but Brian's first example made me realize I left out the anchors! Oops.

 

[mikevh]

If you need to account for decimal point and leading minus sign, /^-?\d+(\.\d+)?$/ will detect a numeric pattern. (Zero or one leading minus, one or more digits, then zero or one groups of a decimal followed by one or more digits.)

Note also that \D means "non-digit", as does the negated character class [^\d] used above.

 

[dozier]

Thanks for the info, mikevh, but for my uses I just needed to detect whether or not it is a positive integer.

 

[mikevh]

Fine. The pattern I suggest will match a simple positive integer, too. If negative numbers or decimals sneak into your data at some future time, it will still work. So it's more flexible. Doesn't hurt to be prepared.