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Re: DIGIT-WEIGHT/DIGITP and funny input bases
- Subject: Re: DIGIT-WEIGHT/DIGITP and funny input bases
- From: Robert W. Kerns <RWK at MIT-MC>
- Date: Tue ,7 Oct 80 04:26:00 EDT
Actually, I think this all is the wrong division of labor. I really thing what
we want is DIGITP and INPUT-FIXNUM. DIGITP simply tells you whether a
character is a digit in the current or supplied base, and INPUT-FIXNUM, takes a
first argument of a SEQUENCE of CHARACTERS, and an optional second argument
like DIGITP. I can't think of any reason why anybody would want to know the
digit weight of a single digit (other than to implement INPUT-FIXNUM), but of
course you can always ask INPUT-FIXNUM to do the conversion.
On a more general level, would take a sequence of characters and an optional
base. INPUT-NUMBER would return the number that the sequence of characters
represents, or () if it is not a valid number representation. INPUT-NUMBER
would handle any valid LISP representation for FLONUM's, FIXNUMs, including
such funny things as 1_5 and such if they're still in the language, ROMAN if
your LISP has ROMAN, CHINEESE if you've got that.
A parser would collect digits and pass them off to INPUT-FIXNUM when it got
them all. I don't see any reason right off why anybody would really want to
deal with the individual weights of individual characters. Does anybody have
any examples where you would?