5 ms·

Likewise in Common Lisp, arguably much more easily.

by reikonomusha 9y ago

systems 9y ago
how ... macros?
- stevelosh 9y ago
  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.
- TeMPOraL 9y ago
  Macros, or (eval-when (:compile-toplevel) [your code here]). Caveats apply.
mhh__ 9y ago
There is no macro needed here. You just write the code, then execute it at compile time. This is designed properly, it's not any where near as hacky as C++'s constexpr
- junke 9y ago
  No need for macros, eval-when is a special operator designed for this: (eval-when (:compile-toplevel) ...) You can also have read-time macros or load-time values, depending on what you need.
rep_movsd 9y ago
Well LISP has no distinction between meta-programming and programming. so as long as you like parens, you can do anything

Likewise in Common Lisp, arguably much more easily.

systems 9y ago

how ... macros?

stevelosh 9y ago
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.
TeMPOraL 9y ago
Macros, or (eval-when (:compile-toplevel) [your code here]). Caveats apply.

mhh__ 9y ago

There is no macro needed here. You just write the code, then execute it at compile time. This is designed properly, it's not any where near as hacky as C++'s constexpr

junke 9y ago
No need for macros, eval-when is a special operator designed for this: (eval-when (:compile-toplevel) ...) You can also have read-time macros or load-time values, depending on what you need.

rep_movsd 9y ago

Well LISP has no distinction between meta-programming and programming. so as long as you like parens, you can do anything