ENH: Remove type number ordering assumptions in CanCastSafely, ScalarKinds, and CanCoerceScalar

Also add print_coercion_tables.py to aid when refactoring
type casting/coercion/promotion.

1 files changed, 79 insertions, 0 deletions

diff --git a/numpy/testing/print_coercion_tables.py b/numpy/testing/print_coercion_tables.py
new file mode 100755
index 000000000..0c8a87d9a
--- /dev/null
+++ b/numpy/testing/print_coercion_tables.py
@@ -0,0 +1,79 @@
+#!/usr/bin/env python
+"""Prints type-coercion tables for the built-in NumPy types"""
+
+import numpy as np
+
+# Generic object that can be added, but doesn't do anything else
+class GenericObject:
+    def __init__(self, v):
+        self.v = v
+
+    def __add__(self, other):
+        return self
+
+    def __radd__(self, other):
+        return self
+
+def print_cancast_table(ntypes):
+    print 'X',
+    for char in ntypes: print char,
+    print
+    for row in ntypes:
+        print row,
+        for col in ntypes:
+            print int(np.can_cast(row, col)),
+        print
+
+def print_coercion_table(ntypes, inputfirstvalue, inputsecondvalue, firstarray):
+    print '+',
+    for char in ntypes: print char,
+    print
+    for row in ntypes:
+        if row == 'O':
+            rowtype = GenericObject
+        else:
+            rowtype = np.obj2sctype(row)
+
+        print row,
+        for col in ntypes:
+            if col == 'O':
+                coltype = GenericObject
+            else:
+                coltype = np.obj2sctype(col)
+            try:
+                if firstarray:
+                    rowvalue = np.array([rowtype(inputfirstvalue)], dtype=rowtype)
+                else:
+                    rowvalue = rowtype(inputfirstvalue)
+                colvalue = coltype(inputsecondvalue)
+                value = np.add(rowvalue,colvalue)
+                if isinstance(value, np.ndarray):
+                    char = value.dtype.char
+                else:
+                    char = np.dtype(type(value)).char
+            except ValueError:
+                char = '!'
+            except OverflowError:
+                char = '@'
+            except TypeError:
+                char = '#'
+            print char,
+        print
+
+print "can cast"
+print_cancast_table(np.typecodes['All'])
+print
+print "In these tables, ValueError is '!', OverflowError is '@', TypeError is '#'"
+print
+print "scalar + scalar"
+print_coercion_table(np.typecodes['All'], 0, 0, False)
+print
+print "scalar + neg scalar"
+print_coercion_table(np.typecodes['All'], 0, -1, False)
+print
+print "array + scalar"
+print_coercion_table(np.typecodes['All'], 0, 0, True)
+print
+print "array + neg scalar"
+print_coercion_table(np.typecodes['All'], 0, -1, True)
+