& not properly exported?

[TsarFox]

Hey,

So the following works:

(in-package :esrap)
(parse '(and (& #\a) #\a) "a")

And so does

(esrap:parse '(and (esrap::& #\a) #\a) "a")

But this does not:

(esrap:parse '(and (& #\a) #\a) "a")

Fails with a "The function COMMON-LISP-USER::& is undefined." This is different behavior than, say + or *.

My apologies if I'm misunderstanding how Esrap is supposed to work.

[scymtym]

Fails with a "The function COMMON-LISP-USER::& is undefined." This is different behavior than, say + or *.

There are multiple things to unpack:

• Esrap treats expressions of the form (SYMBOL …) as "semantic predicates" which involve calling the function named by SYMBOL when SYMBOL is not one of the built-in operators. That's why the error message is "The function COMMON-LISP-USER::& is undefined.".
• + and * are actually cl:+ and cl:*. These symbols are used for multiple things (they name functions, * is used in type specifiers). Esrap uses them (and others such as cl:and and cl:or) as parsing-related operators.
• & on the other hand is not a symbol in the common-lisp package (same for !, ? and ~). As a consequence, if you write your code in the common-lisp-user package, & is read as comon-lisp-user::& which is not a symbol Esrap knows about.

You should be able to refer to the Esrap operator as esrap:&. Using esrap::& (i.e. two colons) should not be necessary since the symbol is exported from the esrap package.

[TsarFox]

I see, thanks for the explanation!