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The only explanation I saw was that C++ standards guys were horrified by the idea of unpredictable side effects as a result of initialization of a struct. I th

The only explanation I saw was that C++ standards guys were horrified by the idea of unpredictable side effects as a result of initialization of a struct. I think C++ though is adding them. What I'd like in c is designated function parameters. // these the same bar(.a = 10, .b = 12); bar(.b = 12, .a = 10);

saagarjha 5y ago
I suspect that to many C++ programmers, most initializations of structs have unpredictable side effects because of how complex they are ;)
wott 5y ago
You can somewhat fake it by replacing your functions parameters list with a single struct parameter. struct bar_arguments { int a, b; }; int bar(struct bar_arguments args) { return 2*args.a + args.b;} #define bar(...) bar((struct bar_arguments) {__VA_ARGS__}) // usage (will print 32 three times) printf("%d\n", bar(10, 12)); printf("%d\n", bar(.a = 10, .b = 12)); printf("%d\n", bar(.b = 12, .a = 10)); The main drawback is that all parameters are now optional: it will not complain if you forget to assign all parameters, it will silently set them to 0 :-/ printf("%d\n", bar(10)); printf("%d\n", bar(.a = 10)); printf("%d\n", bar(.b = 12)); will print 20, 20 and 12. You can change those "default values", but then calling the function with regular positional parameters is impaired :-/
gumby 5y ago
> The only explanation I saw was that C++ standards guys were horrified by the idea of unpredictable side effects as a result of initialization of a struct. I don't understand. How would struct or class initialization be any different from simply doing, say, `for (auto& a : { x, y, z }) frob (a);` which is perfectly legal?
- Gibbon1 5y ago
  I didn't mention. I think the thought was with designated initializers the order of initialization is what? The order of the elements of the struct? Or the order where it's initialized. In C probably matters little as side effects are usually blatant. C++ I think cryptic side effects are common.

saagarjha 5y ago

I suspect that to many C++ programmers, most initializations of structs have unpredictable side effects because of how complex they are ;)

wott 5y ago

You can somewhat fake it by replacing your functions parameters list with a single struct parameter. struct bar_arguments { int a, b; }; int bar(struct bar_arguments args) { return 2*args.a + args.b;} #define bar(...) bar((struct bar_arguments) {__VA_ARGS__}) // usage (will print 32 three times) printf("%d\n", bar(10, 12)); printf("%d\n", bar(.a = 10, .b = 12)); printf("%d\n", bar(.b = 12, .a = 10)); The main drawback is that all parameters are now optional: it will not complain if you forget to assign all parameters, it will silently set them to 0 :-/ printf("%d\n", bar(10)); printf("%d\n", bar(.a = 10)); printf("%d\n", bar(.b = 12)); will print 20, 20 and 12. You can change those "default values", but then calling the function with regular positional parameters is impaired :-/

gumby 5y ago

> The only explanation I saw was that C++ standards guys were horrified by the idea of unpredictable side effects as a result of initialization of a struct. I don't understand. How would struct or class initialization be any different from simply doing, say, `for (auto& a : { x, y, z }) frob (a);` which is perfectly legal?

Gibbon1 5y ago
I didn't mention. I think the thought was with designated initializers the order of initialization is what? The order of the elements of the struct? Or the order where it's initialized. In C probably matters little as side effects are usually blatant. C++ I think cryptic side effects are common.