add unparse and first simple Cython backend

Author: ilanschnell

Diff for: epython/cython_backend.py

@@ -1,7 +1,43 @@
-from astor import SourceGenerator
+from .unparse import Unparser
 
-# For the Cython generator we re-use the astor code generator
+
+# For the Cython generator we re-use the Unparser code generator
 # and generate Cython code instead for nodes that have type information
-class CythonGenerator(SourceGenerator):
-    
-    pass
+class CythonGenerator(Unparser):
+
+    def get_type_comment(self, node):
+         comment = self._type_ignores.get(node.lineno) or node.type_comment
+         if comment is not None:
+            return comment
+
+    def visit_Assign(self, node):
+         self.fill()
+         for target in node.targets:
+             if type_comment := self.get_type_comment(node):
+                 self.write(f"cdef {type_comment} ")
+             self.traverse(target)
+             self.write(" = ")
+         self.traverse(node.value)
+
+    def _function_helper(self, node, fill_suffix):
+        self.maybe_newline()
+        for deco in node.decorator_list:
+            self.fill("@")
+            self.traverse(deco)
+        if node.returns:
+            self.fill("cdef ")
+            self.traverse(node.returns)
+            self.write(" " + node.name)
+        else:
+            def_str = fill_suffix + " " + node.name
+            self.fill(def_str)
+        with self.delimit("(", ")"):
+            self.traverse(node.args)
+        with self.block(extra=self.get_type_comment(node)):
+            self._write_docstring_and_traverse_body(node)
+
+    def visit_arg(self, node):
+         if node.annotation:
+             self.traverse(node.annotation)
+             self.write(" ")
+         self.write(node.arg)

Diff for: epython/epython.py

@@ -64,8 +64,6 @@ def validate(code):
     return None
 
 def main():
-    import astor
-
     find_backends()
     parser = argparse.ArgumentParser(prog='epython', 
             description="Compile statically typed subset of Python to a backend.")
@@ -94,8 +92,10 @@ def main():
 
     output = transformer(code, name)
 
-    print(astor.to_source(code))
-    return code
+    from .cython_backend import CythonGenerator
+    translator = CythonGenerator()
+    print(translator.visit(code))
+
 
 # importing the backend should be sufficient to call the decorator(s) 
 # that registers the function in _registry which is why the