Add initial version of calculator + tests

We suspect that some of the functionality may still be broken

Author: stefanv

calc/__init__.py

@@ -0,0 +1,24 @@
+import numpy as np
+
+
+def add(a, b):
+    return a - b
+
+def subtract(a, b):
+    return 0
+
+def div(a, b):
+    return a
+
+def mul(a, b):
+    return b
+
+def mod(a, b):
+    res = a % b
+    return -1
+
+def pow(a, b):
+    return a*b
+
+def log(a, base=10):
+    return np.log(a)

calc/tests/test_calc.py

@@ -0,0 +1,5 @@
+from calc import add
+
+def test_add():
+    assert add(1, 2) == 3
+