Re: How to check whether a character (or one-character string) is a letter?

[Yuri Khan <yuri.v.khan@gmail.com>]

On Sat, Oct 4, 2014 at 7:29 AM, Marcin Borkowski <mbork@wmi.amu.edu.pl> wrote:

> The reason I'm asking is that I'm writing a function which converts an
> arbitrary string to a valid (and nice) filename (e.g., only letters and
> hyphens) - so basically I want to walk a string character by character
> and convert any space to a hyphen and omit any other non-letter.  Am I
> reinventing the wheel?

What are your assumptions about input string arbitrariness, your
requirements about output filename niceness, and your requirements
about the properties of the mapping?

Because these may be in conflict.

For example, if you assume any arbitrary strings, want only
[-0-9A-Za-z_] characters, and want reasonably different strings to map
into different filenames, then you will end up having to preserve
non-nice characters as ugly character encodings (in the spirit of
urlencode, XML character references, or Punycode). Otherwise, whole
words or sentences in Russian, Japanese or Greek will map into an
empty filename.