issymb : string -> bool

SYNOPSIS
Tests if a one-character string is a symbol other than bracket or separator.

DESCRIPTION
The call issymb s tests whether the first character of string s (normally it is the only character) is ``symbolic''. This means that it is one of the usual ASCII characters but is not alphanumeric, not an underscore or prime character, and is also not one of the two separators `,' or `;' nor any bracket, parenthesis or curly brace. More explicitly, the set of symbolic characters is: 
  \ ! @ # $ % ^ & * - + | \ \ < = > / ? ~ . :

FAILURE CONDITIONS
Fails if the string is empty.

SEE ALSO
isalnum, isalpha, isbra, isnum, issep, isspace.