Data commit

Task/Identity-matrix/Python/identity-matrix-1.py

@@ -0,0 +1,11 @@
+def identity(size):
+    matrix = [[0]*size for i in range(size)]
+    #matrix = [[0] * size] * size    #Has a flaw. See http://stackoverflow.com/questions/240178/unexpected-feature-in-a-python-list-of-lists
+
+    for i in range(size):
+        matrix[i][i] = 1
+
+    for rows in matrix:
+        for elements in rows:
+            print elements,
+        print ""

Task/Identity-matrix/Python/identity-matrix-2.py

@@ -0,0 +1,61 @@
+'''Identity matrices by maps and equivalent list comprehensions'''
+
+import operator
+
+
+# idMatrix :: Int -> [[Int]]
+def idMatrix(n):
+    '''Identity matrix of order n,
+       expressed as a nested map.
+    '''
+    eq = curry(operator.eq)
+    xs = range(0, n)
+    return list(map(
+        lambda x: list(map(
+            compose(int)(eq(x)),
+            xs
+        )),
+        xs
+    ))
+
+
+# idMatrix3 :: Int -> [[Int]]
+def idMatrix2(n):
+    '''Identity matrix of order n,
+       expressed as a nested comprehension.
+    '''
+    xs = range(0, n)
+    return ([int(x == y) for x in xs] for y in xs)
+
+
+# TEST ----------------------------------------------------
+def main():
+    '''
+        Identity matrix of dimension five,
+        by two different routes.
+    '''
+    for f in [idMatrix, idMatrix2]:
+        print(
+            '\n' + f.__name__ + ':',
+            '\n\n' + '\n'.join(map(str, f(5))),
+        )
+
+
+# GENERIC -------------------------------------------------
+
+# compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
+def compose(g):
+    '''Right to left function composition.'''
+    return lambda f: lambda x: g(f(x))
+
+
+# curry :: ((a, b) -> c) -> a -> b -> c
+def curry(f):
+    '''A curried function derived
+       from an uncurried function.'''
+    return lambda a: lambda b: f(a, b)
+
+
+# MAIN ---
+if __name__ == '__main__':
+    main()

Task/Identity-matrix/Python/identity-matrix-3.py

@@ -0,0 +1,11 @@
+>>> def identity(size):
+...     return {(x, y):int(x == y) for x in range(size) for y in range(size)}
+...
+>>> size = 4
+>>> matrix = identity(size)
+>>> print('\n'.join(' '.join(str(matrix[(x, y)]) for x in range(size)) for y in range(size)))
+1 0 0 0
+0 1 0 0
+0 0 1 0
+0 0 0 1
+>>>

Task/Identity-matrix/Python/identity-matrix-4.py

@@ -0,0 +1 @@
+np.mat(np.eye(size))