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C has beyond useless “macros”, they should not be compared with Rust’s, that are actually useful.

by kaba0 3y ago

jimbob45 3y ago
While that’s true, preprocessors are pretty trivial to write these days if you want macros that the language doesn’t support. Racket excels at this.
- sanxiyn 3y ago
  Which preprocessor do you recommend for writing C?
  - jimbob45 3y ago
    https://stackoverflow.com/a/3685576 https://stackoverflow.com/a/3685576 There’s one approach. I wouldn’t personally recommend using macros outside of include guards and file inclusion. Still, if you need more functionality, the methods exist.
  - bsder 3y ago
    None. Use an actual different language. Ada, Rust, Zig, D, Lisp/Scheme/Racket, Tcl, Forth, etc. ... something other than C. Don't preprocess C into a slightly broken other language that you wish it were. Use C as C, or use something else.
foldr 3y ago
C's macros are primitive and unsafe but by no means useless. Here's a somewhat silly example from embedded programming. I wanted to embed the bitmaps of a small set of characters for use on a bitmapped monochrome display. It was easy to define macros CHAR_GRID, _ and X such that e.g. const uint8_t zero[] = { CHAR_GRID( _,X,X,X,_, X,_,_,_,X, X,_,_,X,X, X,_,X,_,X, X,X,_,_,X, X,_,_,_,X, _,X,X,X,_ ) }; desugared to a column-major array of 5 bytes. #define CHAR_GRID(c1r1, c2r1, c3r1, c4r1, c5r1, \ c1r2, c2r2, c3r2, c4r2, c5r2, c1r3, c2r3, c3r3, c4r3, c5r3, c1r4, c2r4, c3r4, c4r4, c5r4, c1r5, c2r5, c3r5, c4r5, c5r5, c1r6, c2r6, c3r6, c4r6, c5r6, c1r7, c2r7, c3r7, c4r7, c5r7) \ c1r1 | (c1r2 << 1) | (c1r3 << 2) | (c1r4 << 3) | (c1r5 << 4) | (c1r6 << 5) | (c1r7 << 6), \ c2r1 | (c2r2 << 1) | (c2r3 << 2) | (c2r4 << 3) | (c2r5 << 4) | (c2r6 << 5) | (c2r7 << 6), \ c3r1 | (c3r2 << 1) | (c3r3 << 2) | (c3r4 << 3) | (c3r5 << 4) | (c3r6 << 5) | (c3r7 << 6), \ c4r1 | (c4r2 << 1) | (c4r3 << 2) | (c4r4 << 3) | (c4r5 << 4) | (c4r6 << 5) | (c4r7 << 6), \ c5r1 | (c5r2 << 1) | (c5r3 << 2) | (c5r4 << 3) | (c5r5 << 4) | (c5r6 << 5) | (c5r7 << 6)
lenkite 3y ago
Something like the Flecs ECS (https://www.flecs.dev/flecs/ https://www.flecs.dev/flecs/) which makes Rust's Bevy team jealous makes extensive use of C's "useless macros".

C has beyond useless “macros”, they should not be compared with Rust’s, that are actually useful.

by kaba0 3y ago

C has beyond useless “macros”, they should not be compared with Rust’s, that are actually useful.

While that’s true, preprocessors are pretty trivial to write these days if you want macros that the language doesn’t support. Racket excels at this.

sanxiyn 3y ago
Which preprocessor do you recommend for writing C?
- jimbob45 3y ago
  https://stackoverflow.com/a/3685576 https://stackoverflow.com/a/3685576 There’s one approach. I wouldn’t personally recommend using macros outside of include guards and file inclusion. Still, if you need more functionality, the methods exist.
- bsder 3y ago
  None. Use an actual different language. Ada, Rust, Zig, D, Lisp/Scheme/Racket, Tcl, Forth, etc. ... something other than C. Don't preprocess C into a slightly broken other language that you wish it were. Use C as C, or use something else.

foldr 3y ago

C's macros are primitive and unsafe but by no means useless. Here's a somewhat silly example from embedded programming. I wanted to embed the bitmaps of a small set of characters for use on a bitmapped monochrome display. It was easy to define macros CHAR_GRID, _ and X such that e.g. const uint8_t zero[] = { CHAR_GRID( _,X,X,X,_, X,_,_,_,X, X,_,_,X,X, X,_,X,_,X, X,X,_,_,X, X,_,_,_,X, _,X,X,X,_ ) }; desugared to a column-major array of 5 bytes. #define CHAR_GRID(c1r1, c2r1, c3r1, c4r1, c5r1, \ c1r2, c2r2, c3r2, c4r2, c5r2, c1r3, c2r3, c3r3, c4r3, c5r3, c1r4, c2r4, c3r4, c4r4, c5r4, c1r5, c2r5, c3r5, c4r5, c5r5, c1r6, c2r6, c3r6, c4r6, c5r6, c1r7, c2r7, c3r7, c4r7, c5r7) \ c1r1 | (c1r2 << 1) | (c1r3 << 2) | (c1r4 << 3) | (c1r5 << 4) | (c1r6 << 5) | (c1r7 << 6), \ c2r1 | (c2r2 << 1) | (c2r3 << 2) | (c2r4 << 3) | (c2r5 << 4) | (c2r6 << 5) | (c2r7 << 6), \ c3r1 | (c3r2 << 1) | (c3r3 << 2) | (c3r4 << 3) | (c3r5 << 4) | (c3r6 << 5) | (c3r7 << 6), \ c4r1 | (c4r2 << 1) | (c4r3 << 2) | (c4r4 << 3) | (c4r5 << 4) | (c4r6 << 5) | (c4r7 << 6), \ c5r1 | (c5r2 << 1) | (c5r3 << 2) | (c5r4 << 3) | (c5r5 << 4) | (c5r6 << 5) | (c5r7 << 6)

lenkite 3y ago

Something like the Flecs ECS (https://www.flecs.dev/flecs/ https://www.flecs.dev/flecs/) which makes Rust's Bevy team jealous makes extensive use of C's "useless macros".