Correctness first:
# man isdigit
ISALPHA(3) Linux Programmer's Manual ISALPHA(3)
NAME
isalnum, isalpha, isascii, isblank, iscntrl, isdigit,
isgraph, islower, isprint, ispunct, isspace, isupper,
isxdigit - character classification routines
SYNOPSIS
for(i=0; istrlen(s); i++)... has quadratic run time.
Not a problem in current code (it is never called on
more than LINE_LENGTH (1024) bytes, thus touches 'only' 500 Kbytes at
most), but it is not a good practice anyway. Especially since we don't need
strlen() here _at all_.
I talked about
