Add fallback expressions for Sqrt and Exp functions (#220)

m2cgen/assemblers/fallback_expressions.py

@@ -30,6 +30,20 @@ def tanh(expr):
             tanh_expr))
 
 
+def sqrt(expr, to_reuse=False):
+    return ast.PowExpr(
+        base_expr=expr,
+        exp_expr=ast.NumVal(0.5),
+        to_reuse=to_reuse)
+
+
+def exp(expr, to_reuse=False):
+    return ast.PowExpr(
+        base_expr=ast.NumVal(2.71828182845904523536028747135),
+        exp_expr=expr,
+        to_reuse=to_reuse)
+
+
 def sigmoid(expr, to_reuse=False):
     neg_expr = ast.BinNumExpr(ast.NumVal(0), expr, ast.BinNumOpType.SUB)
     exp_expr = ast.ExpExpr(neg_expr)

m2cgen/interpreters/interpreter.py

@@ -121,17 +121,21 @@ def interpret_vector_val(self, expr, **kwargs):
         return self._cg.vector_init(nested)
 
     def interpret_exp_expr(self, expr, **kwargs):
-        if self.exponent_function_name is NotImplemented:
-            raise NotImplementedError("Exponent function is not provided")
         self.with_math_module = True
+        if self.exponent_function_name is NotImplemented:
+            return self._do_interpret(
+                fallback_expressions.exp(expr.expr, to_reuse=expr.to_reuse),
+                **kwargs)
         nested_result = self._do_interpret(expr.expr, **kwargs)
         return self._cg.function_invocation(
             self.exponent_function_name, nested_result)
 
     def interpret_sqrt_expr(self, expr, **kwargs):
-        if self.sqrt_function_name is NotImplemented:
-            raise NotImplementedError("Sqrt function is not provided")
         self.with_math_module = True
+        if self.sqrt_function_name is NotImplemented:
+            return self._do_interpret(
+                fallback_expressions.sqrt(expr.expr, to_reuse=expr.to_reuse),
+                **kwargs)
         nested_result = self._do_interpret(expr.expr, **kwargs)
         return self._cg.function_invocation(
             self.sqrt_function_name, nested_result)

m2cgen/interpreters/visual_basic/interpreter.py

@@ -68,13 +68,6 @@ def interpret_pow_expr(self, expr, **kwargs):
         return self._cg.infix_expression(
             left=base_result, right=exp_result, op="^")
 
-    def interpret_sqrt_expr(self, expr, **kwargs):
-        return self.interpret_pow_expr(
-            ast.PowExpr(base_expr=expr.expr,
-                        exp_expr=ast.NumVal(0.5),
-                        to_reuse=expr.to_reuse),
-            **kwargs)
-
     def interpret_tanh_expr(self, expr, **kwargs):
         self.with_tanh_expr = True
         return super(

tests/test_fallback_expressions.py

@@ -25,3 +25,33 @@ def score(input):
 """
 
     assert_code_equal(interpreter.interpret(expr), expected_code)
+
+
+def test_sqrt_fallback_expr():
+    expr = ast.SqrtExpr(ast.NumVal(2.0))
+
+    interpreter = PythonInterpreter()
+    interpreter.sqrt_function_name = NotImplemented
+
+    expected_code = """
+import math
+def score(input):
+    return math.pow(2.0, 0.5)
+"""
+
+    assert_code_equal(interpreter.interpret(expr), expected_code)
+
+
+def test_exp_fallback_expr():
+    expr = ast.ExpExpr(ast.NumVal(2.0))
+
+    interpreter = PythonInterpreter()
+    interpreter.exponent_function_name = NotImplemented
+
+    expected_code = """
+import math
+def score(input):
+    return math.pow(2.718281828459045, 2.0)
+"""
+
+    assert_code_equal(interpreter.interpret(expr), expected_code)