Merge pull request #10033 from JuliaLang/jcb/diffdimerr

throw error on invalid dimension argument for diff
JuliaLang · Feb 3, 2015 · e8355d4 · e8355d4
2 parents aabd23b + f4de7c5
commit e8355d4
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diff --git a/base/linalg/generic.jl b/base/linalg/generic.jl
@@ -45,8 +45,10 @@ diff(a::AbstractVector) = [ a[i+1] - a[i] for i=1:length(a)-1 ]
 function diff(A::AbstractMatrix, dim::Integer)
     if dim == 1
         [A[i+1,j] - A[i,j] for i=1:size(A,1)-1, j=1:size(A,2)]
-    else
+    elseif dim == 2
         [A[i,j+1] - A[i,j] for i=1:size(A,1), j=1:size(A,2)-1]
+    else
+        throw(ArgumentError("dimension dim must be 1 or 2, got $dim"))
     end
 end
 

diff --git a/test/linalg1.jl b/test/linalg1.jl
@@ -302,3 +302,12 @@ end # for eltya
 #6941
 #@test (ones(10^7,4)*ones(4))[3] == 4.0
 
+# test diff, throw ArgumentError for invalid dimension argument
+let X = [3  9   5;
+         7  4   2;
+         2  1  10]
+    @test diff(X,1) == [4  -5 -3; -5  -3  8]
+    @test diff(X,2) == [6 -4; -3 -2; -1 9]
+    @test_throws ArgumentError diff(X,3)
+    @test_throws ArgumentError diff(X,-1)
+end