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"Also, division by zero is an runtime operation error, it is not really a type error. The division operation doesn't fail because it violated the type system, i

by fao_ 8y ago

"Also, division by zero is an runtime operation error, it is not really a type error. The division operation doesn't fail because it violated the type system, it fails because you can't mathematically divide by zero." Zero is a different type from the type that consists of integers above N.

slededit 8y ago
Its an interesting concept. Addition or subtraction now would have to dynamically return either a zero type or a non-zero type. I suppose the type system could force you to check and handle the zero case. In reality I think it would be too cumbersome. Division by zero is a relatively rare flaw and zero agnostic math on integers is common. I'd love to hear about any languages that do this.
- joshuamorton 8y ago
  Not necessarily, additional and subtraction just return int, but you can define other operations over subsets of ints that return nonzero. Rust does something similar, floats by default can be NaN, but you can write a non-NaN float that just panics if it's Nan and then ignore the possibility of Nan in parts of your system.
smadge 8y ago
What is "the type that consists of integers above N?" If N = -1, then 0 is in the set of integers greater than N. I think it makes more sense to say that division is a function F × (F - {0}) → F where F is a field. F is not the same set/type as F without 0. I think in the context of computer languages this would be called a refinement type. (https://en.wikipedia.org/wiki/Refinement_type https://en.wikipedia.org/wiki/Refinement_type)
tremon 8y ago
Can you show a language that implements your concept of "integers above N" consistently? I fail to see how such a type would be remotely useful in the context of addition/subtraction operators. I think Ada comes closest to your definition with allowing modular and derived integer types, but the former does include 0 and I'm not sure if the latter even allows division.

by fao_ 8y ago

slededit 8y ago

Its an interesting concept. Addition or subtraction now would have to dynamically return either a zero type or a non-zero type. I suppose the type system could force you to check and handle the zero case. In reality I think it would be too cumbersome. Division by zero is a relatively rare flaw and zero agnostic math on integers is common. I'd love to hear about any languages that do this.

joshuamorton 8y ago
Not necessarily, additional and subtraction just return int, but you can define other operations over subsets of ints that return nonzero. Rust does something similar, floats by default can be NaN, but you can write a non-NaN float that just panics if it's Nan and then ignore the possibility of Nan in parts of your system.

smadge 8y ago

What is "the type that consists of integers above N?" If N = -1, then 0 is in the set of integers greater than N. I think it makes more sense to say that division is a function F × (F - {0}) → F where F is a field. F is not the same set/type as F without 0. I think in the context of computer languages this would be called a refinement type. (https://en.wikipedia.org/wiki/Refinement_type https://en.wikipedia.org/wiki/Refinement_type)

tremon 8y ago

Can you show a language that implements your concept of "integers above N" consistently? I fail to see how such a type would be remotely useful in the context of addition/subtraction operators. I think Ada comes closest to your definition with allowing modular and derived integer types, but the former does include 0 and I'm not sure if the latter even allows division.