Ranges

When you need to match a range of numbers, the range syntax is your best friend. Character ranges (e.g. ['0'-'7']) are only able to match a single digit; the range syntax has no such limitation:

let octet = range '0'-'255';

# ipv4 address
octet ('.' octet){3}

This generates a regular expression that is both correct and as efficient as possible, since it never requires backtracking. If you’re curious, here’s the regex the range '0'-'255' compiles to:

0|1[0-9]{0,2}|2(?:[0-4][0-9]?|5[0-5]?|[6-9])?|[3-9][0-9]?

Different bases #

Pomsky can generate ranges in various bases. For example, to match hexadecimal numbers in a certain range, you might write:

range '10F'-'FFFF' base 16

Leading zeroes #

If you wish to support leading zeros, this is easy to achieve by putting '0'* in front:

'0'* range '0'-'1024'

If the number should have a certain length, with leading zeroes added when necessary, Pomsky has a special syntax for this:

range '0000'-'1024'

This matches numbers in the specified range with exactly 4 digits, such as 0110 or 0026.