Documentation not showing all methods

documentation

#1

This is probably a stupid question but when I type ?\ in the REPL (Julia 0.6), I get the following docstrings for \(x, y) and \(A, B):

\(x, y)

  Left division operator: multiplication of y by the inverse of x on the left.
  Gives floating-point results for integer arguments.

  julia> 3 \ 6
  2.0
  
  julia> inv(3) * 6
  2.0
  
  julia> A = [1 2; 3 4]; x = [5, 6];
  
  julia> A \ x
  2-element Array{Float64,1}:
   -4.0
    4.5
  
  julia> inv(A) * x
  2-element Array{Float64,1}:
   -4.0
    4.5

  \(A, B)

  Matrix division using a polyalgorithm. For input matrices A and B, the
  result X is such that A*X == B when A is square. The solver that is used
  depends upon the structure of A. If A is upper or lower triangular (or
  diagonal), no factorization of A is required and the system is solved with
  either forward or backward substitution. For non-triangular square matrices,
  an LU factorization is used.

  For rectangular A the result is the minimum-norm least squares solution
  computed by a pivoted QR factorization of A and a rank estimate of A based
  on the R factor.

  When A is sparse, a similar polyalgorithm is used. For indefinite matrices,
  the LDLt factorization does not use pivoting during the numerical
  factorization and therefore the procedure can fail even for invertible
  matrices.

     Example
    ≡≡≡≡≡≡≡≡≡

  julia> A = [1 0; 1 -2]; B = [32; -4];
  
  julia> X = A \ B
  2-element Array{Float64,1}:
   32.0
   18.0
  
  julia> A * X == B
  true

In the Julia documentation, however, I could only find the first method: https://docs.julialang.org/en/release-0.6/stdlib/linalg/#Standard-Functions-1

Is that on purpose to not clutter the documentation? Or is \(A,B) documented somewhere else?


#2

I’m not sure, but there is a change in the documentation from v0.5 to v0.6. In v0.5 the first definition is under the mathematics section of the documentation, while the second is under the linear algebra section. In v0.6, both the mathematics and linear algebra sections have the first definition.

I couldn’t find the second definition anywhere in the v0.6 documentation online. It’s possible that the docs changed in v0.6 and the second definition just didn’t get removed, or that the online docs are incorrect. It makes more sense to me that the online docs are wrong. Either way, the documentation online and in the REPL should match so one of those needs to be changed.


#3

Thanks. I’ll open an issue.

Edit: here

Edit 2: Fixed in https://github.com/JuliaLang/julia/pull/24307