VectorProvider

An F# library that generates dimension-typed vectors and arithmetic operators for them. This library is an erased type provider - during compilation all Vector<_> types are unwrapped to array<int> types. This gives compile-time checking of vector dimensions with the same runtime performance of non-length checked arrays.

open VectorProvider

type Vec3 = Vector<3u>
let pt3d = Vec3 (1, 2, 3)
let one = pt3d.Dimension1
pt3d.Dimension2 <- 5
let four = pt3d.Dimension4 // Compiler error FS0039: The type 'Vector<3>' does not define the field, constructor or member 'Dimension4'
pt3d.Dimension4 <- 7 // Compiler error FS0039: The type 'Vector<3>' does not define the field, constructor or member 'Dimension4'

type Vec4 = Vector<4u>
let pt4dError = Vec4 (1, 2, 3) // Compiler error FS0505: The member or object constructor 'Vector,dimension="4"' does not take 3 arguments
let pt4d = Vec4 (0, 0, 0, 0)
pt4d.Dimension4 <- 1

let pt1 = Vec3 (1, 2, 3)
let pt2 = Vec3 (4, 5, 6)
let pt3 = pt1 +. pt2 // = Vec3 (5, 7, 9)
let pt4 = pt2 -. pt1 // = Vec3 (3, 3, 3)
let pt5 = -.pt1 // = Vec3 (-1, -2, -3)

let pt6 = pt3d +. pt4d // Compiler error FS0001: This expression was expected to have type 'Vector<3>' but here has type 'Vector<4>'

To do

• Add more vector arithmetic operators
• Generalize to types other than int
  • This may require RFC FS-1023 to implement in a generalized way
• Improve testing
  • FsCheck views a Vector<_> as the type after erasure (array<int>), so property-based testing via FsCheck passes in arrays that are not length-checked. For now FsCheck is used to generate int * int * int values, which can be piped to the Vector<3u> constructor to create test data
  • The current tests only involve Vector<3u> - is it possible to have a bug in Vector<n> but not Vector<m>?