ndarray: implement fill and fill! (#297)

It serve as an API corresponds to Python's `mx.nd.full()`

NEWS.md

@@ -4,6 +4,13 @@
 
 * `deepcopy` for NDArray (#273)
 
+* `fill` and `fill!` for NDArray (#TBD)
+  An API correspond to Python's `mx.nd.full()`
+
+    * `fill(x, dims, ctx=cpu())`
+    * `fill(x, dims...)`
+    * `fill!(x, arr::NDArray)`
+
 ## API Changes
 
 * `reshape` of NDArray share the same interface with Base (#272).

src/ndarray.jl

@@ -703,6 +703,31 @@ function /(arg0 :: NDArray, arg :: Real)
 end
 
 
+"""
+    fill!(x, arr::NDArray)
+
+Create an `NDArray` filled with the value `x`, like `Base.fill`.
+"""
+function fill!(x, arr::NDArray)
+  arr[:] = x
+  arr
+end
+
+"""
+    fill(x, dims, ctx=cpu())
+    fill(x, dims...)
+
+Create an `NDArray` filled with the value `x`, like `Base.fill`.
+"""
+function fill{N}(x, dims::NTuple{N, Integer}, ctx::Context=cpu())
+  arr = empty(typeof(x), dims, ctx)
+  arr[:] = x
+  arr
+end
+
+fill(x, dims::Integer...) = fill(x, dims)
+
+
 """
 Manipulating as Julia Arrays
 ----------------------------

test/unittest/ndarray.jl

@@ -413,6 +413,42 @@ function test_reshape()
     @test size(C) == (50, 4)
 end
 
+function test_fill()
+  info("NDArray::fill")
+  thresh = 1e8
+
+  let x = mx.fill(42, 2, 3, 4)
+    @test eltype(x) == Int
+    @test size(x) == (2, 3, 4)
+    @test copy(x) == fill(42, 2, 3, 4)
+  end
+
+  let x = mx.fill(Float32(42), 2, 3, 4)
+    @test eltype(x) == Float32
+    @test size(x) == (2, 3, 4)
+    @test reldiff(copy(x), fill(Float32(42), 2, 3, 4)) < thresh
+  end
+
+  let x = mx.fill(42, (2, 3, 4))
+    @test eltype(x) == Int
+    @test size(x) == (2, 3, 4)
+    @test copy(x) == fill(42, 2, 3, 4)
+  end
+
+  let x = mx.fill(Float32(42), (2, 3, 4))
+    @test eltype(x) == Float32
+    @test size(x) == (2, 3, 4)
+    @test reldiff(copy(x), fill(Float32(42), 2, 3, 4)) < thresh
+  end
+
+  info("NDArray::fill!::arr")
+  let x = mx.fill!(42, mx.zeros(2, 3, 4))
+    @test eltype(x) == Float32
+    @test size(x) == (2, 3, 4)
+    @test reldiff(copy(x), fill(Float32(42), 2, 3, 4)) < thresh
+  end
+end  # function test_fill
+
 function test_kwargs()
   info("NDArray::kwargs")
   dims1 = (2,3,4)
@@ -454,6 +490,7 @@ end
   test_nd_as_jl()
   test_dot()
   test_reshape()
+  test_fill()
   test_kwargs()
   test_show()
 end