I might try this... it wasn't actually named is_digit_char; I was actually writing a token parser for a "monadic" parser combinator library in Hy and my functio

I might try this... it wasn't actually named is_digit_char; I was actually writing a token parser for a "monadic" parser combinator library in Hy and my function was more idiomatically named there, integer-char? (after the CLHS function DIGIT-CHAR-P).