add squeeze and unsqueeze (#235)

* add addInnerDim and addOuterDim

* rework with numir like API

source/mir/algorithm/iteration.d

@@ -60,7 +60,6 @@ import std.traits;
 
 @optmath:
 
-
 /+
 Bitslice representation for accelerated bitwise algorithm.
 1-dimensional contiguousitslice can be split into three chunks: head bits, body chunks, and tail bits.

source/mir/ndslice/package.d

@@ -161,11 +161,13 @@ $(TR $(TDNW $(SUBMODULE topology) $(BR)
         $(SUBREF topology, ReshapeError)
         $(SUBREF topology, retro)
         $(SUBREF topology, slide)
+        $(SUBREF topology, squeeze)
         $(SUBREF topology, stairs)
         $(SUBREF topology, stride)
         $(SUBREF topology, subSlices)
         $(SUBREF topology, triplets)
         $(SUBREF topology, universal)
+        $(SUBREF topology, unsqueeze)
         $(SUBREF topology, unzip)
         $(SUBREF topology, windows)
         $(SUBREF topology, zip)

source/mir/ndslice/topology.d

@@ -67,7 +67,9 @@ $(TR $(TH Function Name) $(TH Description))
 
 $(T2 blocks, n-dimensional slice composed of n-dimensional non-overlapping blocks. If the slice has two dimensions, it is a block matrix.)
 $(T2 diagonal, 1-dimensional slice composed of diagonal elements)
-$(T2 reshape, New slice with changed dimensions for the same data)
+$(T2 reshape, New slice view with changed dimensions)
+$(T2 squeeze, New slice view of an n-dimensional slice with dimension removed)
+$(T2 unsqueeze, New slice view of an n-dimensional slice with a dimension added)
 $(T2 windows, n-dimensional slice of n-dimensional overlapping windows. If the slice has two dimensions, it is a sliding window.)
 
 )
@@ -96,7 +98,7 @@ $(SUBREF slice, Slice.shape), and $(SUBREF slice, Slice.elementCount).
 
 License:   $(HTTP boost.org/LICENSE_1_0.txt, Boost License 1.0).
 Copyright: Copyright © 2016-, Ilya Yaroshenko
-Authors:   Ilya Yaroshenko
+Authors:   Ilya Yaroshenko, Shigeki Karita (original numir code)
 
 Sponsors: Part of this work has been sponsored by $(LINK2 http://symmetryinvestments.com, Symmetry Investments) and Kaleidic Associates.
 
@@ -3918,7 +3920,7 @@ template byDim(Dimensions...)
             n-dimensional slice ipacked to allow iteration by dimension
         +/
         @optmath auto byDim(Iterator, size_t N, SliceKind kind)
-                                       (Slice!(Iterator, N, kind) slice)
+            (Slice!(Iterator, N, kind) slice)
         {
             import mir.ndslice.topology : ipack;
             import mir.ndslice.internal : DimensionsCountCTError;
@@ -4240,6 +4242,171 @@ version(mir_test) unittest
     assert(x == slice);
 }
 
+/++
+Constructs a new view of an n-dimensional slice with dimension `axis` removed.
+
+Throws:
+    `AssertError` if the length of the corresponding dimension doesn' equal 1.
+Params:
+    axis = dimension to remove, if it is single-dimensional
+    slice = n-dimensional slice
+Returns:
+    new view of a slice with dimension removed
+See_also: $(LREF unsqueeze), $(LREF iota).
++/
+Slice!(Iterator, N - 1, kind != Canonical ? kind : axis == 0 ? Universal : N == 2 ? Contiguous : kind)
+    squeeze(sizediff_t axis = 0, Iterator, size_t N, SliceKind kind)
+    (Slice!(Iterator, N, kind) slice)
+    if (-sizediff_t(N) <= axis && axis < sizediff_t(N) && N > 1)
+in {
+    assert(slice._lengths[axis < 0 ? N + axis : axis] == 1);
+}
+do {
+    import mir.utility: swap;
+    enum sizediff_t a = axis < 0 ? N + axis : axis;
+    typeof(return) ret;
+    foreach (i; 0 .. a)
+        ret._lengths[i] = slice._lengths[i];
+    foreach (i; a + 1 .. N)
+        ret._lengths[i - 1] = slice._lengths[i];
+    static if (kind == Universal)
+    {
+        foreach (i; 0 .. a)
+            ret._strides[i] = slice._strides[i];
+        foreach (i; a + 1.. N)
+            ret._strides[i - 1] = slice._strides[i];
+    }
+    else
+    static if (kind == Canonical)
+    {
+        static if (a == 0)
+        {
+            foreach (i; 0 .. N - 1)
+                ret._strides[i] = slice._strides[i];
+        }
+        else
+        {
+            foreach (i; 0 .. a - 1)
+                ret._strides[i] = slice._strides[i];
+            foreach (i; a .. N - 1)
+                ret._strides[i - 1] = slice._strides[i];
+        }
+    }
+    swap(ret._iterator, slice._iterator);
+    return ret;
+}
+
+///
+unittest
+{
+    import mir.ndslice.topology : iota;
+    import mir.ndslice.allocation : slice;
+
+    // [[0, 1, 2]] -> [0, 1, 2]
+    assert([1, 3].iota.squeeze == [3].iota);
+    // [[0], [1], [2]] -> [0, 1, 2]
+    assert([3, 1].iota.squeeze!1 == [3].iota);
+    assert([3, 1].iota.squeeze!(-1) == [3].iota);
+
+    assert([1, 3].iota.canonical.squeeze == [3].iota);
+    assert([3, 1].iota.canonical.squeeze!1 == [3].iota);
+    assert([3, 1].iota.canonical.squeeze!(-1) == [3].iota);
+
+    assert([1, 3].iota.universal.squeeze == [3].iota);
+    assert([3, 1].iota.universal.squeeze!1 == [3].iota);
+    assert([3, 1].iota.universal.squeeze!(-1) == [3].iota);
+
+    assert([1, 3, 4].iota.squeeze == [3, 4].iota);
+    assert([3, 1, 4].iota.squeeze!1 == [3, 4].iota);
+    assert([3, 4, 1].iota.squeeze!(-1) == [3, 4].iota);
+
+    assert([1, 3, 4].iota.canonical.squeeze == [3, 4].iota);
+    assert([3, 1, 4].iota.canonical.squeeze!1 == [3, 4].iota);
+    assert([3, 4, 1].iota.canonical.squeeze!(-1) == [3, 4].iota);
+
+    assert([1, 3, 4].iota.universal.squeeze == [3, 4].iota);
+    assert([3, 1, 4].iota.universal.squeeze!1 == [3, 4].iota);
+    assert([3, 4, 1].iota.universal.squeeze!(-1) == [3, 4].iota);
+}
+
+/++
+Constructs a view of an n-dimensional slice with a dimension added at `axis`. Used
+to unsqueeze a squeezed slice.
+
+Params:
+    slice = n-dimensional slice
+    axis = dimension to be unsqueezed (add new dimension), default values is 0, the first dimension
+Returns:
+    unsqueezed n+1-dimensional slice of the same slice kind
+See_also: $(LREF squeeze), $(LREF iota).
++/
+Slice!(Iterator, N + 1, kind) unsqueeze(Iterator, size_t N, SliceKind kind)
+    (Slice!(Iterator, N, kind) slice, sizediff_t axis = 0)
+in {
+    assert(-sizediff_t(N + 1) <= axis && axis <= sizediff_t(N));
+}
+do {
+    import mir.utility: swap;
+    typeof(return) ret;
+    if (axis < 0)
+    {
+        axis += N + 1;
+    }
+    foreach (i; 0 .. axis)
+        ret._lengths[i] = slice._lengths[i];
+    ret._lengths[axis] = 1;
+    foreach (i; axis .. N)
+        ret._lengths[i + 1] = slice._lengths[i];
+    static if (kind == Universal)
+    {
+        foreach (i; 0 .. axis)
+            ret._strides[i] = slice._strides[i];
+        foreach (i; axis .. N)
+            ret._strides[i + 1] = slice._strides[i];
+    }
+    else
+    static if (kind == Canonical)
+    {
+        if (axis == 0)
+        {
+            ret._strides[0] = 1;
+            foreach (i; 1 .. N)
+                ret._strides[i] = slice._strides[i - 1];
+        }
+        else
+        {
+            foreach (i; 1 .. axis)
+                ret._strides[i - 1] = slice._strides[i - 1];
+            foreach (i; axis .. N)
+                ret._strides[i + 0] = slice._strides[i - 1];
+        }
+    }
+    swap(ret._iterator, slice._iterator);
+    return ret;
+}
+
+///
+version (mir_test) 
+@safe pure nothrow @nogc
+unittest
+{
+    // [0, 1, 2] -> [[0, 1, 2]]
+    assert([3].iota.unsqueeze == [1, 3].iota);
+
+    assert([3].iota.universal.unsqueeze == [1, 3].iota);
+    assert([3, 4].iota.unsqueeze == [1, 3, 4].iota);
+    assert([3, 4].iota.canonical.unsqueeze == [1, 3, 4].iota);
+    assert([3, 4].iota.universal.unsqueeze == [1, 3, 4].iota);
+
+    // [0, 1, 2] -> [[0], [1], [2]]
+    assert([3].iota.unsqueeze(-1) == [3, 1].iota);
+
+    assert([3].iota.universal.unsqueeze(-1) == [3, 1].iota);
+    assert([3, 4].iota.unsqueeze(-1) == [3, 4, 1].iota);
+    assert([3, 4].iota.canonical.unsqueeze(-1) == [3, 4, 1].iota);
+    assert([3, 4].iota.universal.unsqueeze(-1) == [3, 4, 1].iota);
+}
+
 /++
 Field (element's member) projection.