3 ms·

I think because it's ambiguous with unary plus (a = +b), since C isn't supposed to have significant whitespace in most circumstances.

by vgel 3y ago

kazinator 3y ago
But originally there wasn't a += or =+ lexical token! Those things were scanned as separate tokens, and could be written = +. So that is problematic; If {a}{=}{-}{b} means a = a - b, then you have no way to write a = -b without parentheses like a = (-b).
tom_ 3y ago
You also run into problems with a=*p and a=-b, which are perhaps more likely.
- zeusk 3y ago
  But they could've fixed that by going a=(*p) and a=(-b); Kind of how we use (*p)->next instead of *p->next where p is node_t**
  - kdmccormick 3y ago
    That seems a little backwards and barbaric, though right? Imagine if we had to watch out for this as a common pitfall: // BUG! Actually subtracts x from current val of neg_x. neg_x = -x; Even moreso, how would these two lines behave? Would they differ in semantics? n = -5 n =- 5 Overall, -= is just so much less ambiguous. EDIT: To your point about ->, I personally think C would be better if: *p->next parsed as: (*p)->next instead of: *(p->next) but maybe now I'm not thinking through all the parsing impliciations :)
    - zeusk 3y ago
      As you note in your edit; we already have to watch for that pitfall :) so really the best way out is to be as verbose as possible imo; a = a + c or auto nodep = *nodepp; nodep->next; Compilers and compute performance have grown to make the difference negligible for code output and compilation times but they definitely take a lot of mental complexity out of such scenarios (anything helps when grokking 10k+ lines of code).
    - tom_ 3y ago
      I've found struct fields that are pointers far more common than pointers to pointers to structs, so if nothing else it feels like *(p->target) is a more widely useful interpretation of *p->target than (*p)->target would be. Regarding "n = -5", it would presumably be interpreted as "n=(-5)", same as today. Operators don't have spaces in them. So "n- -5" is "n-(-5)", rather than "n--5" (not valid).

I think because it's ambiguous with unary plus (a = +b), since C isn't supposed to have significant whitespace in most circumstances.

by vgel 3y ago

I think because it's ambiguous with unary plus (a = +b), since C isn't supposed to have significant whitespace in most circumstances.

kazinator 3y ago

But originally there wasn't a += or =+ lexical token! Those things were scanned as separate tokens, and could be written = +. So that is problematic; If {a}{=}{-}{b} means a = a - b, then you have no way to write a = -b without parentheses like a = (-b).

tom_ 3y ago

You also run into problems with a=*p and a=-b, which are perhaps more likely.

zeusk 3y ago
But they could've fixed that by going a=(*p) and a=(-b); Kind of how we use (*p)->next instead of *p->next where p is node_t**
- kdmccormick 3y ago
  That seems a little backwards and barbaric, though right? Imagine if we had to watch out for this as a common pitfall: // BUG! Actually subtracts x from current val of neg_x. neg_x = -x; Even moreso, how would these two lines behave? Would they differ in semantics? n = -5 n =- 5 Overall, -= is just so much less ambiguous. EDIT: To your point about ->, I personally think C would be better if: *p->next parsed as: (*p)->next instead of: *(p->next) but maybe now I'm not thinking through all the parsing impliciations :)
  - zeusk 3y ago
    As you note in your edit; we already have to watch for that pitfall :) so really the best way out is to be as verbose as possible imo; a = a + c or auto nodep = *nodepp; nodep->next; Compilers and compute performance have grown to make the difference negligible for code output and compilation times but they definitely take a lot of mental complexity out of such scenarios (anything helps when grokking 10k+ lines of code).
  - tom_ 3y ago
    I've found struct fields that are pointers far more common than pointers to pointers to structs, so if nothing else it feels like *(p->target) is a more widely useful interpretation of *p->target than (*p)->target would be. Regarding "n = -5", it would presumably be interpreted as "n=(-5)", same as today. Operators don't have spaces in them. So "n- -5" is "n-(-5)", rather than "n--5" (not valid).