Calling CHARCODE from within a function

[pamoroso]

I'm trying to figure out how to pass a character to a funtion as an argument and in turn pass the argument to CHARCODE from within the function, like in this test:

4_ (DEFINEQ (FOO (NLAMBDA (CHAR) (CHARCODE CHAR))))
(FOO)
5_ (FOO A)
BAD CHARACTER SPECIFICATION
CHAR

Why do I get the error? Examining the code of CHARCODE and CHARCODE.DECODE didn't ring any bells.

[pamoroso]

The error is actually a good clue as CHARCODE is treating the CHAR litatom as its argument, not the value of the CHAR parameter of FOO. So how do I obtain the intended behavior?

[rmkaplan]

Use CHARCODE.DECODE, that's the function that evaluates its argument, CHARCODE quotes its argument. (CHARCODE SPACE) is equivalent to (CHARCODE.DECODE (QUOTE SPACE)), but typically more convenient. Note that SELCHARQ is also a macro that expands to a SELECTQ applying CHARCODE.DECODE to each of its selection keys, also convenient.

…

On Dec 28, 2025, at 9:31 AM, Paolo Amoroso ***@***.***> wrote: The error is actually a good clue as CHARCODE is treating the CHAR litatom as its argument, not the value of the CHAR parameter of FOO. So how do I obtain the intended behavior? — Reply to this email directly, view it on GitHub <#2429 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AQSTUJLVP3HHYRX63OTBZWD4EAHWLAVCNFSM6AAAAACQFWM55KVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTKMZVG43DMNA>. You are receiving this because you are subscribed to this thread.

[pamoroso]

Using CHARCODE.DECODE does the trick, thanks.

[masinter]

(CHARCODE SPACE) is equivalent to (CHARCODE.DECODE (QUOTE SPACE)), but typically more convenient.

It also isn't quite equivalent becauses the lookup of the symbol SPACE to find 20 happens at compile(macro expansion) time, while the code using CHARCODE.DCODE calls CHARCODE.DECODE at runtime.