Vanilla macros are one option. (defmacro html (string) (some-html-parser-library:parse string)) Or you could use a function and a compiler macro to make

Vanilla macros are one option. (defmacro html (string) (some-html-parser-library:parse string)) Or you could use a function and a compiler macro to make it more of an optimization -- if the argument is known at compile-time just parse it then, otherwise wait til runtime: (defun html (string) (some-html-parser-library:parse string)) (define-compiler-macro html (&whole form string) (if (constantp string) `',(some-html-parser-library:parse string) form)) Actual example, using `string-upcase` to stand in for an HTML parsing library: (defun html (string) (string-upcase string)) (define-compiler-macro html (&whole form string) (if (constantp string) `',(string-upcase string) form)) (defun foo (arg) (print (html arg)) (print (html "compile-time")) nil) (foo "run-time") ; "RUN-TIME" ; "COMPILE-TIME" (disassemble 'foo) ; disassembly for FOO ; Size: 128 bytes. Origin: #x10106A207D ; 7D: 498B4C2460 MOV RCX, [R12+96] ; thread.binding-stack-pointer ; no-arg-parsing entry point ; 82: 48894DF8 MOV [RBP-8], RCX ; 86: 488D5C24F0 LEA RBX, [RSP-16] ; 8B: 4883EC18 SUB RSP, 24 ; 8F: 488B55F0 MOV RDX, [RBP-16] ; 93: 488B0576FFFFFF MOV RAX, [RIP-138] ; #<SB-KERNEL:FDEFN HTML> ; 9A: B902000000 MOV ECX, 2 ; 9F: 48892B MOV [RBX], RBP ; A2: 488BEB MOV RBP, RBX ; A5: FF5009 CALL QWORD PTR [RAX+9] ; A8: 480F42E3 CMOVB RSP, RBX ; AC: 488D5C24F0 LEA RBX, [RSP-16] ; B1: 4883EC18 SUB RSP, 24 ; B5: 488B055CFFFFFF MOV RAX, [RIP-164] ; #<SB-KERNEL:FDEFN COMMON-LISP:PRINT> ; BC: B902000000 MOV ECX, 2 ; C1: 48892B MOV [RBX], RBP ; C4: 488BEB MOV RBP, RBX ; C7: FF5009 CALL QWORD PTR [RAX+9] ; CA: 488D5C24F0 LEA RBX, [RSP-16] ; CF: 4883EC18 SUB RSP, 24 ; D3: 488B1546FFFFFF MOV RDX, [RIP-186] ; "COMPILE-TIME" ; DA: 488B0537FFFFFF MOV RAX, [RIP-201] ; #<SB-KERNEL:FDEFN COMMON-LISP:PRINT> ; E1: B902000000 MOV ECX, 2 ; E6: 48892B MOV [RBX], RBP ; E9: 488BEB MOV RBP, RBX ; EC: FF5009 CALL QWORD PTR [RAX+9] ; EF: BA17001020 MOV EDX, 537919511 ; F4: 488BE5 MOV RSP, RBP ; F7: F8 CLC ; F8: 5D POP RBP ; F9: C3 RET ; FA: 0F0B10 BREAK 16 ; Invalid argument count trap `html` is only called once, to handle the call that isn't known at compile time.