3 ms·
> In this case, a function of 0 arguments and a function of 1 trivial unit argument are visibly different even though their total effect on the state is the sam
by lmm 2y ago
> In this case, a function of 0 arguments and a function of 1 trivial unit argument are visibly different even though their total effect on the state is the same. After all, we're talking about theory of computation and so it better be able to handle computations as they are actually performed at the low level, too.
You don't have to push anything for the unit values on the stack though, their representation doesn't take up any space. Just like if you're passing a big argument (like a large integer, or a struct passed by value) it might take multiple registers or a lot of space in your stack frame, there's no 1:1 correspondence between arguments and stack space.
> you want to special-case handling of unit so that passing it as an argument would not touch %rdi, and assigning a unit to a value should not write any registers
This shouldn't need to be a special case though. For each datatype you have a way of mapping it to/from some number of registers, and for the unit type that number of registers is 0 and that mapping is a no-op.
- Joker_vD 2y ago> their representation doesn't take up any space. One of the way to represent them doesn't take up any space. But if you want to e.g. have a generic function of e.g. (T,U,V) -> V type (that is, with no monomorphization in your compiler) then either your units have to take space (otherwise the layout of (unit,int,bool) is different from (int,int,bool) and the same), or you'll have to pass around type descriptors when invoking generic functions. Which many, many implementors of static languages rather wouldn't do unless absolutely necessary.
- lmm 2y ago> if you want to e.g. have a generic function of e.g. (T,U,V) -> V type (that is, with no monomorphization in your compiler) then either your units have to take space (otherwise the layout of (unit,int,bool) is different from (int,int,bool) and the same), or you'll have to pass around type descriptors when invoking generic functions. You have that problem already though surely, as T might be bigger than an int, or want to be passed in a floating-point register, or both.