Generate character sequences from POSIX Bracket Expressions

a bracket expression matches any character among those listed between the opening and closing square brackets. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, based upon the system’s native character set. For example, ‘[0-9]’ is equivalent to ‘[0123456789]’ ~ GNU Awk manual

Bracket expressions are often used to limit searches, regular expressions and filters. But sometimes you need to have the range of characters expanded and explicitly listed; this library helps do that.

gen, _ := bechars.New()
rng, _ := gen.Generate("[:print:]")
fmt.Println(rng) // => " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~"

// Unicode characters
rng, _ = gen.Generate("[\u0e010-2]")
fmt.Println(rng) // => "ก012"

rng, _ = gen.Generate("[:punct:]")
fmt.Println(rng) // => "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~]"

The generator can also be configured:

gen, _ := bechars.New(MinRune('a'), MaxRune('z'))
rng, _ := gen.Generate("[^:cntrl::punct:]")
fmt.Println(rng) // => "abcdefghijklmnopqrstuvwxyz"

See the tests for more examples.