Raphael wrote: Does antlr build the AST for us automatically by option{output=AST;}? Or do I have to make the tree myself? If it does, then how to spit out the nodes on that AST? No, the parser does not know what you want as root and as leaves for each parser rule, so you’ll have … Read more
What interests me is the Compile() method. Does it somehow produce real MSIL? Yes. The Compile method runs a visitor over the lambda body block and generates IL dynamically for each subexpression. If you’re interested in learning how to spit IL yourself, see this “Hello World” example of how to use Lightweight Codegen. (I note … Read more
You can make any of these work. I prefer the union layout, because then all nodes have “the same” layout. [You may find it useful to have a “child sublist” option, e.g., and arbitarily big, dynamic array of children, instead of having left- or right-leaning lists.] You are going to find that this issue isn’t … Read more
Wikipedia has a great overview of how the Visitor pattern works, although the sample implementation that they use is in Java. You can easily port that to Python, though, no? Basically, you want to implement a mechanism for double dispatch. Each node in your AST would need to implement an accept() method (NOT a visit() … Read more
GraphQL is two things: A query language A Type System When a GraphQL server receives a query to process it generally comes in as a single String. This string must be split into meaningful sub-strings (tokenization) and parsed into a representation that the machine understands. This representation is called an abstract syntax tree, or AST. … Read more
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