13 ms·

int f(float x) { return (int )x; }

by yuubi 12y ago

int f(float x) { return *(int *)x; }

vidarh 12y ago
That program refuses to compile not because you can't cast to/from arbitrary types in C, but because you don't make your intent explicit (assuming I read what you tried to do correctly). Try this: int f(float x) { return *(int *)&x; } On one hand you demonstrate that C cares a tiny little bit about type, but mostly because of implicit numeric conversions rather than any serious attempt at stropping you from bad casting. I do agree with the point that C isn't "typeless" in any real sense, though.
- jeorgun 12y ago
  I think the original was intentional. If C refuses to let you cast from a non-pointer to a pointer, then it is in fact enforcing some (small) degree of type-safety.
  - vidarh 12y ago
    The reason I assumed it was not, is that obtaining the bitwise representation of a float is something people actually often ask for (and my variation is not the "right" way to do so). You may be right C does not refuse to let you cast from a non-pointer to a pointer either, though. It just forces you to be slightly more devious in this case: return *(int **)&x; Though I think the implicit conversions that force some of these contortions (e.g. "(int *)(int)x" compiles, but does not return an integer pointer with the address equal to the bit pattern of "x" interpreted as an integer, but the integer portion of the float reinterpreted as a pointer) are more convincing demonstration that C is not typeless in a meaningful way in my opinion, as they also mean identical statements will give different results depending on the types of the variables.
    - vegedor 12y ago
      Well, you are laying of the safety belt there, don't complain afterwards. It make sense to me in some cases, so i won't even argue.
- deleted 12y ago
  [deleted]
- yuubi 12y ago
  The intent was to show that (at least one implementation of) C does stop a completely nonsensical cast from float to pointer, not to demonstrate anything semi-sensible like getting the bits of a float.

int f(float x) { return *(int *)x; }

by yuubi 12y ago

int f(float x) { return *(int *)x; }

That program refuses to compile not because you can't cast to/from arbitrary types in C, but because you don't make your intent explicit (assuming I read what you tried to do correctly). Try this: int f(float x) { return *(int *)&x; } On one hand you demonstrate that C cares a tiny little bit about type, but mostly because of implicit numeric conversions rather than any serious attempt at stropping you from bad casting. I do agree with the point that C isn't "typeless" in any real sense, though.

jeorgun 12y ago
I think the original was intentional. If C refuses to let you cast from a non-pointer to a pointer, then it is in fact enforcing some (small) degree of type-safety.
- vidarh 12y ago
  The reason I assumed it was not, is that obtaining the bitwise representation of a float is something people actually often ask for (and my variation is not the "right" way to do so). You may be right C does not refuse to let you cast from a non-pointer to a pointer either, though. It just forces you to be slightly more devious in this case: return *(int **)&x; Though I think the implicit conversions that force some of these contortions (e.g. "(int *)(int)x" compiles, but does not return an integer pointer with the address equal to the bit pattern of "x" interpreted as an integer, but the integer portion of the float reinterpreted as a pointer) are more convincing demonstration that C is not typeless in a meaningful way in my opinion, as they also mean identical statements will give different results depending on the types of the variables.
  - vegedor 12y ago
    Well, you are laying of the safety belt there, don't complain afterwards. It make sense to me in some cases, so i won't even argue.
deleted 12y ago
[deleted]
yuubi 12y ago
The intent was to show that (at least one implementation of) C does stop a completely nonsensical cast from float to pointer, not to demonstrate anything semi-sensible like getting the bits of a float.