Fix findmin/findmax to return cartesian indices for BitMatrix

For consistency with other AbstractArray types.
The call to keys is optimized out by the compiler for vectors thanks to
@inbounds.

base/bitarray.jl

@@ -1510,7 +1510,6 @@ function findprev(testf::Function, B::BitArray, start::Integer)
 end
 #findlast(testf::Function, B::BitArray) = findprev(testf, B, 1)  ## defined in array.jl
 
-
 function findmax(a::BitArray)
     isempty(a) && throw(ArgumentError("BitArray must be non-empty"))
     m, mi = false, 1
@@ -1519,9 +1518,9 @@ function findmax(a::BitArray)
     for i = 1:length(ac)
         @inbounds k = trailing_zeros(ac[i])
         ti += k
-        k == 64 || return (true, ti)
+        k == 64 || return (true, @inbounds keys(a)[ti])
     end
-    return m, mi
+    return m, @inbounds keys(a)[mi]
 end
 
 function findmin(a::BitArray)
@@ -1532,13 +1531,13 @@ function findmin(a::BitArray)
     for i = 1:length(ac)-1
         @inbounds k = trailing_ones(ac[i])
         ti += k
-        k == 64 || return (false, ti)
+        k == 64 || return (false, @inbounds keys(a)[ti])
     end
     l = Base._mod64(length(a)-1) + 1
     @inbounds k = trailing_ones(ac[end] & Base._msk_end(l))
     ti += k
-    k == l || return (false, ti)
-    return m, mi
+    k == l || return (false, @inbounds keys(a)[ti])
+    return (m, @inbounds keys(a)[mi])
 end
 
 # findall helper functions

test/arrayops.jl

@@ -567,6 +567,11 @@ end
     @test isnan(findmax([NaN, NaN, 0.0/0.0])[1])
     @test findmax([NaN, NaN, 0.0/0.0])[2] == 1
 
+    # Check that cartesian indices are returned for matrices
+    @test argmax([10 12; 9 11]) === CartesianIndex(1, 2)
+    @test argmin([10 12; 9 11]) === CartesianIndex(2, 1)
+    @test findmax([10 12; 9 11]) === (12, CartesianIndex(1, 2))
+    @test findmin([10 12; 9 11]) === (9, CartesianIndex(2, 1))
 end
 
 @testset "permutedims" begin

test/bitarray.jl

@@ -1523,6 +1523,8 @@ timesofar("linalg")
     for b1 in [falses(v1), trues(v1),
                BitArray([1,0,1,1,0]),
                BitArray([0,0,1,1,0]),
+               BitArray([1 0; 1 1]),
+               BitArray([0 0; 1 1]),
                bitrand(v1)]
         @check_bit_operation findmin(b1)
         @check_bit_operation findmax(b1)