Add scal!(a,X) (JuliaLang#40446)

Author: dbrueg

stdlib/LinearAlgebra/src/blas.jl

@@ -218,15 +218,21 @@ end
 
 """
     scal!(n, a, X, incx)
+    scal!(a, X)
 
 Overwrite `X` with `a*X` for the first `n` elements of array `X` with stride `incx`. Returns `X`.
+
+If `n` and `incx` are not provided, `length(X)` and `stride(X,1)` are used.
 """
 function scal! end
 
 """
     scal(n, a, X, incx)
+    scal(a, X)
 
 Return `X` scaled by `a` for the first `n` elements of array `X` with stride `incx`.
+
+If `n` and `incx` are not provided, `length(X)` and `stride(X,1)` are used.
 """
 function scal end
 
@@ -242,9 +248,12 @@ for (fname, elty) in ((:dscal_,:Float64),
                   n, DA, DX, incx)
             DX
         end
+
+        scal!(DA::$elty, DX::AbstractArray{$elty}) = scal!(length(DX),DA,DX,stride(DX,1))
     end
 end
 scal(n, DA, DX, incx) = scal!(n, DA, copy(DX), incx)
+scal(DA, DX) = scal!(DA, copy(DX))
 
 ## dot
 

stdlib/LinearAlgebra/test/blas.jl

@@ -514,6 +514,11 @@ end
         BLAS.axpby!(elty(2), x, elty(3), y)
         @test y == WrappedArray(elty[19, 50, 30, 56])
         @test BLAS.iamax(x) == 2
+
+        M = fill(elty(1.0), 3, 3)
+        BLAS.scal!(elty(2), view(M,:,2))
+        BLAS.scal!(elty(3), view(M,3,:))
+        @test M == elty[1. 2. 1.; 1. 2. 1.; 3. 6. 3.]
     # Level 2
         A = WrappedArray(elty[1 2; 3 4])
         x = WrappedArray(elty[1, 2])