AST means Abstract Syntax Tree, which is basically an abstract representation of code / any syntactic structure. A transformation is an action modifying this tree (i.e. transforming the existing AST to a new AST). For more information have a look here: http://en.wikipedia.org/wiki/Abstract_syntax_tree
I looked at the other answers; it appears people are doing backflips to get around the problems of computing line numbers, when your real problem is one of modifying the code. That suggests the baseline machinery is not helping you the way you really need. If you use a program transformation system (PTS), you could … Read more
The documentation states it is safe, and there is no bug relative to security of literal_eval in the bug tracker, so you can probably assume it is safe. Also, according to the source, literal_eval parses the string to a python AST (source tree), and returns only if it is a literal. The code is never … Read more
The fundamental trick is to recognize that parsing, however accomplished, happens in incremental steps, including the reading of the tokens one by one. At each incremental step, there is an opportunity to build part of the AST by combining AST fragments built by other incremental steps. This is a recursive idea, and it bottoms out … Read more
The method with -cc1 invocation will have problem with includes and recognizing C++. For full-featured parsing, use: clang -Xclang -ast-dump file.cpp
ast.literal_eval (located in ast.py) parses the tree with ast.parse first, then it evaluates the code with quite an ugly recursive function, interpreting the parse tree elements and replacing them with their literal equivalents. Unfortunately the code is not at all expandable, so to add Decimal to the code you need to copy all the code … Read more
The TypeScript parser doesn’t directly produce a tree like that, but you can still use its object model to do all sorts of things. We use it in some tools to do syntax transforms for testing purposes, for example. Here’s a snippet that you can use to print the syntax tree: import ts from “typescript”; … Read more
This is based on the Expression Evaluator grammar by Terrence Parr. The grammar for this example: grammar Expr002; options { output=AST; ASTLabelType=CommonTree; // type of $stat.tree ref etc… } prog : ( stat )+ ; stat : expr NEWLINE -> expr | ID ‘=’ expr NEWLINE -> ^(‘=’ ID expr) | NEWLINE -> ; expr … Read more
ast.visit — unless you override it in a subclass, of course — when called to visit an ast.Node of class foo, calls self.visit_foo if that method exists, otherwise self.generic_visit. The latter, again in its implementation in class ast itself, just calls self.visit on every child node (and performs no other action). So, consider, for example: … Read more
1.You can take a look at AST explorer. An online tool to explore the ASTs generated by more than 10 parsers. It is a good tool to learn AST tree of a language. AST explorer source at Github.com. 2.Also you can paste your js code into JavaScript AST visualizer and click “show ast” button, you … Read more