compiler: factorize operation of NodeTransformer on statement lists

artiq/compiler/fold_constants.py

@@ -1,7 +1,7 @@
 import ast, operator
 
 from artiq.language import units
-from artiq.compiler.tools import value_to_ast
+from artiq.compiler.tools import value_to_ast, make_stmt_transformer
 
 class _NotConstant(Exception):
 	pass
@@ -79,7 +79,4 @@ class _ConstantFolder(ast.NodeTransformer):
 			return node
 		return result
 
-def fold_constants(stmts):
+fold_constants = make_stmt_transformer(_ConstantFolder)
-	constant_folder = _ConstantFolder()
-	new_stmts = [constant_folder.visit(stmt) for stmt in stmts]
-	stmts[:] = new_stmts

artiq/compiler/tools.py

@@ -23,3 +23,10 @@ def value_to_ast(value):
 					args=[ast.Num(value.amount), ast.Name("base_"+value.unit.name+"_unit", ast.Load())],
 					keywords=[], starargs=None, kwargs=None)
 		return None
+
+def make_stmt_transformer(transformer_class):
+	def stmt_transformer(stmts):
+		transformer = transformer_class()
+		new_stmts = [transformer.visit(stmt) for stmt in stmts]
+		stmts[:] = new_stmts
+	return stmt_transformer