let tuple = (1.0f32, 2.0f32, 3.0f32, 4.0f32); let a,b,c = tuple.1, tuple.2, tuple.3; // I prefer this. (0-based?) // or: tuple.a, tuple.b, tuple.c, ...z // or: tuple[index]
2014/1/15 Richard Diamond <[email protected]> > Basically the idea here is to support shuffling for SIMD types in a way > that can be easily lowered to IR (LLVM's shufflevector requires the mask be > a vector of constants, so an intrinsic function is out of the question), > however I image this sugar could extend to tuples with multiple types. > > Some examples: > > let vec = (1.0f32, 2.0f32, 3.0f32, 4.0f32); > let all_x = vec -> (0, 0, 0, 0); // perhaps this should be "vec <- (0, 0, > 0, 0)"? > assert_eq!(all_x, (1.0f32, 1.0f32, 1.0f32, 1.0f32)); > let single_x = vec -> (0); > assert_eq!(single_x, (1.0f32)); > > let mut vec = vec; > vec <- (0) = 5.0f32; // set x only > vec <- (1, 2) = (6.0f32, 7.0f32) // set y & z > assert_eq!(vec, (5.0f32, 6.0f32, 7.0f32, 4.0f32)); > > let vec = vec; > // the mask may be arbitrarily long: > assert_eq!(vec -> (0, 1, 2, 3, 0), (5.0f32, 6.0f32, 7.0f32, 4.0f32, > 5.0f32)); > > // leaves vec unchanged > let functional_update = vec -> (0, 1, 3) .. (0.5f32, 1.0f32, 10.0f32); > // functional_update would take it's type from vec > assert_eq!(vec, (5.0f32, 6.0f32, 7.0f32, 4.0f32)); > assert_eq!(functional_update, (0.5f32, 1.0f32, 7.0f32, 10.0f32)); > > A couple of things would need to be disallowed, however: > > let mut vec = vec; > // no duplicate assignments/functional updates: > vec <- (0, 0) = (..); > let _ = vec -> (0, 1, 2, 3, 0) .. (..); > // no out-of-bounds: > vec <- (5, 9000) = (..); > let _ = vec -> (5, 9001); > let _ = vec -> (5, 9002) .. (..); > let _ = vec -> (0, 1, 2, 3, 4) .. (..); > // all mask values must be a const expr: > let mut non_const_expr = 15; > vec <- (non_const_expr) = (..); > let _ = vec -> (non_const_expr) .. (..); > let _ = vec -> (non_const_expr); > // mismatched tuple sizes: > vec <- (0, 1) = (0.0f32, 0.0f32, 0.0f32); > let _ = vec -> (0) .. (0.0f32, 0.0f32); > > AIUI, the notation would be: > tuple_mask : '(' integer [ ',' integer ] * ')' ; > tuple_expr : '(' expr [ ',' expr ] * ')' | > tuple_expr "->" tuple_mask [ ".." tuple_expr ] ? ; > > I'm willing to write this myself, but I'd like some consensus/feedback > regarding ze proposed sugar. > > _______________________________________________ > Rust-dev mailing list > [email protected] > https://mail.mozilla.org/listinfo/rust-dev > > -- by *Liigo*, http://blog.csdn.net/liigo/ Google+ https://plus.google.com/105597640837742873343/
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