Fix array unpacking (pyccel#1793)

Add missing `PythonTuple` cast to fix array unpacking. Fixes pyccel#1792.
Add tests including tests returning slices. Fix C bug returning slices.
Fixes pyccel#1795.

Author: EmilyBourne

CHANGELOG.md

@@ -17,6 +17,8 @@ All notable changes to this project will be documented in this file.
 -   Fix some cases where a Python built-in type is returned in place of a NumPy type.
 -   Stop printing numbers with more decimal digits than their precision.
 -   Allow printing the result of a function returning multiple objects of different types.
+-   #1792 : Fix array unpacking.
+-   #1795 : Fix bug when returning slices in C.
 
 ### Changed
 -   #1720 : functions with the `@inline` decorator are no longer exposed to Python in the shared library.

pyccel/codegen/printing/ccode.py

@@ -2131,8 +2131,7 @@ def _print_AliasAssign(self, expr):
 
         # the below condition handles the case of reassinging a pointer to an array view.
         # setting the pointer's is_view attribute to false so it can be ignored by the free_pointer function.
-        if not self.is_c_pointer(lhs_var) and \
-                isinstance(lhs_var, Variable) and lhs_var.is_ndarray:
+        if isinstance(lhs_var, Variable) and lhs_var.is_ndarray and not lhs_var.is_optional:
             rhs = self._print(rhs_var)
 
             if isinstance(rhs_var, Variable) and rhs_var.is_ndarray:
@@ -2143,12 +2142,12 @@ def _print_AliasAssign(self, expr):
                     return 'transpose_alias_assign({}, {});\n'.format(lhs, rhs)
             else:
                 lhs = self._print(lhs_var)
-                return '{} = {};\n'.format(lhs, rhs)
+                return f'{lhs} = {rhs};\n'
         else:
             lhs = self._print(lhs_address)
             rhs = self._print(rhs_address)
 
-            return '{} = {};\n'.format(lhs, rhs)
+            return f'{lhs} = {rhs};\n'
 
     def _print_For(self, expr):
         self.set_scope(expr.scope)

pyccel/parser/semantic.py

@@ -74,7 +74,7 @@
 from pyccel.ast.headers import FunctionHeader, MethodHeader, Header
 from pyccel.ast.headers import MacroFunction, MacroVariable
 
-from pyccel.ast.internals import PyccelInternalFunction, Slice, PyccelSymbol
+from pyccel.ast.internals import PyccelInternalFunction, Slice, PyccelSymbol, PyccelArrayShapeElement
 from pyccel.ast.itertoolsext import Product
 
 from pyccel.ast.literals import LiteralTrue, LiteralFalse
@@ -3363,7 +3363,7 @@ def _visit_Assign(self, expr):
                         new_lhs.append( self._assign_lhs_variable(l, d_var[i].copy(), rhs, new_expressions, isinstance(expr, AugAssign)) )
                 lhs = PythonTuple(*new_lhs)
 
-            elif d_var['shape'][0]==n:
+            elif d_var['shape'][0]==n or isinstance(d_var['shape'][0], PyccelArrayShapeElement):
                 new_lhs = []
                 new_rhs = []
 
@@ -3372,7 +3372,7 @@ def _visit_Assign(self, expr):
                     new_rhs.append(r)
 
                 lhs = PythonTuple(*new_lhs)
-                rhs = new_rhs
+                rhs = PythonTuple(*new_rhs)
             else:
                 errors.report(WRONG_NUMBER_OUTPUT_ARGS, symbol=expr, severity='error')
                 return None

tests/epyccel/modules/arrays.py

@@ -1718,14 +1718,6 @@ def arr_arange_7(arr : 'int[:,:]'):
     for i in range(n):
         arr[i] = np.arange(i, i+m)
 
-def iterate_slice(i : int):
-    import numpy as np
-    a = np.arange(15)
-    res = 0
-    for ai in a[:i]:
-        res += ai
-    return res
-
 #==============================================================================
 # NUMPY SUM
 #==============================================================================
@@ -1753,3 +1745,32 @@ def multiple_np_linspace():
     y = np.linspace(0, 4, 128)
     z = np.linspace(0, 8, 128)
     return x[0] + y[1] + z[2] + linspace_index
+
+#==============================================================================
+# Iteration
+#==============================================================================
+
+def iterate_slice(i : int):
+    from numpy import arange
+    a = arange(15)
+    res = 0
+    for ai in a[:i]:
+        res += ai
+    return res
+
+@template('T', ['int[:]', 'int[:,:]', 'int[:,:,:]', 'int[:,:](order=F)', 'int[:,:,:](order=F)'])
+def unpack_array(arr : 'T'):
+    x, y, z = arr[:]
+    return x, y, z
+
+def unpack_array_of_known_size():
+    from numpy import array
+    arr = array([1,2,3], dtype='float64')
+    x, y, z = arr[:]
+    return x, y, z
+
+def unpack_array_2D_of_known_size():
+    from numpy import array
+    arr = array([[1,2,3], [4,5,6], [7,8,9]], dtype='float64')
+    x, y, z = arr[:]
+    return x.sum(), y.sum(), z.sum()

tests/epyccel/test_arrays.py

@@ -3647,11 +3647,6 @@ def test_numpy_arange_into_slice(language):
     f2(x)
     np.testing.assert_allclose(x, x_expected, rtol=RTOL, atol=ATOL)
 
-def test_iterate_slice(language):
-    f1 = arrays.iterate_slice
-    f2 = epyccel(f1, language = language)
-    i = randint(2, 10)
-    assert f1(i) == f2(i)
 ##==============================================================================
 ## TEST NESTED ARRAYS INITIALIZATION WITH ORDER C
 ##==============================================================================
@@ -3975,11 +3970,65 @@ def test_array_ndmin_2_order(language):
     check_array_equal(f1(d), f2(d))
     check_array_equal(f1(e), f2(e))
 
+##==============================================================================
+## TEST ITERATION
+##==============================================================================
+
+def test_iterate_slice(language):
+    f1 = arrays.iterate_slice
+    f2 = epyccel(f1, language = language)
+    i = randint(2, 10)
+    assert f1(i) == f2(i)
+
+@pytest.mark.parametrize( 'language', (
+        pytest.param("fortran", marks = [
+            pytest.mark.xfail(reason=("Cannot return a non-contiguous slice. See #1796")),
+            pytest.mark.fortran]),
+        pytest.param("c", marks = pytest.mark.c),
+        pytest.param("python", marks = pytest.mark.python)
+    )
+)
+def test_unpacking(language):
+    f1 = arrays.unpack_array
+    f2 = epyccel(f1, language = language)
+
+    arr = np.arange(3, dtype=int)
+    assert f1(arr) == f2(arr)
+
+    arr = np.arange(12, dtype=int).reshape((3,4))
+    x1, y1, z1 = f1(arr)
+    x2, y2, z2 = f2(arr)
+    check_array_equal(x1, x2)
+    check_array_equal(y1, y2)
+    check_array_equal(z1, z2)
 
-#def teardown_module():
-#    import os, glob
-#    dirname  = os.path.dirname( arrays.__file__ )
-#    pattern  = os.path.join( dirname, '__epyccel__*' )
-#    filelist = glob.glob( pattern )
-#    for f in filelist:
-#        os.remove( f )
+    arr = np.arange(24, dtype=int).reshape((3,4,2))
+    x1, y1, z1 = f1(arr)
+    x2, y2, z2 = f2(arr)
+    check_array_equal(x1, x2)
+    check_array_equal(y1, y2)
+    check_array_equal(z1, z2)
+
+    arr = np.arange(12, dtype=int).reshape((3,4), order='F')
+    x1, y1, z1 = f1(arr)
+    x2, y2, z2 = f2(arr)
+    check_array_equal(x1, x2)
+    check_array_equal(y1, y2)
+    check_array_equal(z1, z2)
+
+    arr = np.arange(24, dtype=int).reshape((3,4,2), order='F')
+    x1, y1, z1 = f1(arr)
+    x2, y2, z2 = f2(arr)
+    check_array_equal(x1, x2)
+    check_array_equal(y1, y2)
+    check_array_equal(z1, z2)
+
+def test_unpacking_of_known_size(language):
+    f1 = arrays.unpack_array_of_known_size
+    f2 = epyccel(f1, language = language)
+    assert f1() == f2()
+
+def test_unpacking_2D_of_known_size(language):
+    f1 = arrays.unpack_array_2D_of_known_size
+    f2 = epyccel(f1, language = language)
+    assert f1() == f2()