CODEWITHSUNDEEP
pythonluacode-generationabstract-syntax-treepretty-print
brubsby
brubsby

Reputation: 478

How do you robustly generate code, given a description of its exact behavior in another language?

I have been reverse engineering a specific black box equation that is part of a system I do not own (do not worry, it's white-hat), in which you can only measure the inputs (a large set of integers) and outputs (two integers).

This system can only be perfectly described as a program/function in which all the input integers are used, and so far I can perfectly describe the behavior by creating a data structure that has named "mathematical terms" in which each named input integer lives, and each term has an ordering for the inputs that it owns. I also have a function that takes the model description, and a set of named inputs, and outputs two integers. So the mapping of lists of input names to program behavior lives in here and in the model description in tandem.

I've been programming the reverse engineering utility in python, but ultimately I want to output a low level lua program that represents this function in a less abstract manner. When there were less terms in the model, it was simple to manually write a "transpiler" from this model (in python) to lua, but as the complexity grows it's painful to rewrite the code generator for new types of terms, especially in an ad-hoc manner.

From reading other questions about similar systems, it seems the very last two steps of this process would be: generating an abstract syntax tree representing my desired program, and giving the ast to a lua prettyprinter to generate the code. But I'm not sure if there's useful abstractions that I'm unaware of that help me generate a lua ast, given my current description of the model.

Upvotes: 1

Views: 131

Answers (1)

Mooshua
Mooshua

Reputation: 539

What you're looking for is an abstract syntax tree, which can define the behavior of a program through a graph. Since each component of an abstract syntax tree is highly compartmentalized (eg, "Add", "Number Constant"...) is it extraordinarily efficient to translate an abstract syntax tree back into a high-level programming language, such as Lua.

Abstract syntax trees are used in many compilers and transpilers, so you will not be digging long to find good examples.

Upvotes: 1

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