Features of this package are defmacro-enhance useable! (I.e. in DEFMACRO! from DEFMACRO-ENHANCE system both sampling expansion and splicing expansion can be used)
This package adds a possibility for macros to inject several forms (not just one) into surrounding macros's body.
CL-SPLICING-MACRO> (defmacro bar (&rest things) "Just a toy macros, that expands into a PLUS" `(+ ,@things)) CL-SPLICING-MACRO> (define-maybe-splicing-macro foo (a b &sample (1 2)) "Just a toy macro that will splice in the body of surrounding macro." `(sprogn ,a ,b)) CL-SPLICING-MACRO> (macroexpand-1 '(bar 1 2 (foo 3 4) 5 6)) (+ 1 2 3 4 5 6) ; enjoy!
Whether a given macros is splicing or not is decided on basis of whether its expansion contains SPROGN in CAR-position, or not. For this to work, we need a "characteristic expansion" of this macros, or a "testing expansion".
New magic word &SAMPLE in macro-lambda-list is used to provide parameters of a macro, that result in generic-enough expansion (against which checks on the structure of the expansion can be made).
Sampling expansion for a given macros, if present, can be obtained with help of TESTING-EXPANSION macros.
CL-SPLICING-MACRO> (define-maybe-sampling-macro my-macro (a &sample (qwerty)) ...) ; define-my-clever-macro CL-SPLICING-MACRO> (if (indeed-clever-expansion-p (testing-expansion my-macro)) do-something-useful)
By default, DEFINE-MAYBE-SAMPLING-MACRO is a wrapper around plain DEFMACRO, but DEFINE-/SAMPLING! macro-construction macros can be used to add sampling feature to your favorite DEFMACRO-like operator (e.g. DEFMACRO! from Let-Over-Lambda).
CL-SPLICING-MACRO> (define-/sampling! def-my-fav-macro-sampling def-my-fav-macro)