Scheme does use ?, and you can in CL if you really want. But CL reserves ? as a programmable reader macro [1]. It is often used, for example, to designate a stand-in domain variable designation in, say an embedded Prolog.
Another reason that CL avoids the "?" convention is that it's "unpronounceable" [2]. CL is the only language spec I've seen that discusses pronunciation; they actually gave thought to how programmers might converse about their code unambiguously [3]. Another manifestation of this is CL's sort-of case-insensitivity [4].
--
[1] The other reserved characters are !, [ ], and { }
[2] Although at least one wag suggested pronouncing it as "eh?", like a good Canadian.
[3] CLtL2 provides quite a bit of this. My fav is a brief excursion into how some hackers pronounce "macrolet" to rhyme with Chevrolet. :)
[4] This is not actually the case, but appears to be true to new Lispers, until they understand that by default, the reader converts everything to upcase.
Did you miss the Hoon language and their pronunciation table that works for other languages too? http://urbit.org/docs/hoon/syntax/ They suggest pronouncing '?' as 'wut'.
http://www.lispworks.com/documentation/lw51/CLHS/Front/X_Per...
Scheme does use ?, and you can in CL if you really want. But CL reserves ? as a programmable reader macro [1]. It is often used, for example, to designate a stand-in domain variable designation in, say an embedded Prolog.
Another reason that CL avoids the "?" convention is that it's "unpronounceable" [2]. CL is the only language spec I've seen that discusses pronunciation; they actually gave thought to how programmers might converse about their code unambiguously [3]. Another manifestation of this is CL's sort-of case-insensitivity [4].
--
[1] The other reserved characters are !, [ ], and { }
[2] Although at least one wag suggested pronouncing it as "eh?", like a good Canadian.
[3] CLtL2 provides quite a bit of this. My fav is a brief excursion into how some hackers pronounce "macrolet" to rhyme with Chevrolet. :)
[4] This is not actually the case, but appears to be true to new Lispers, until they understand that by default, the reader converts everything to upcase.