CODEWITHSUNDEEP
antlrantlr4
Engineer
Engineer

Reputation: 8857

ANTLR4 - Generate code from non-file inputs?

Where do we start to manually build a CST from scratch? Or does ANTLR4 always require the lex/parse process as our input step?

I have some visual elements in my program that represent code structures.

e.g. a square represents a class, while a circle embedded within that square represents a method.

Now I want to turn those into code. How do I use ANTLR4 to do this, at runtime (using ANTLR4.js)? Most of the ANTLR examples seem to rely on lexing and parsing existing code to get to a syntax tree. So rather than:

input code->lex->parse->syntax tree->output code (1)

I want

manually create syntax tree->output code (2)

(Later, as the user adds code to that class and its methods, then ANTLR will be used as in (1).)

EDIT Maybe I'm misunderstanding this. Do I create some custom data structure and then run the parser over it? i.e. write structures to some in-memory format->parse->output code (3)?

Upvotes: 1

Views: 430

Answers (1)

GRosenberg
GRosenberg

Reputation: 6001

IIUC, you could use StringTemplate directly.

By, way of background, Antlr itself builds an in-memory parse-tree and then walks it, incrementally calling StringTemplate to output code snippets qualified by corresponding parse-tree node data. That Antlr uses an internal parse-tree is just a convenience for simplifying walking (since Antlr is built using Antlr).

If you have your own data structure, regardless of its specific implementation, procedurally process it to progressively call ST templates to emit the corresponding code. And, you can directly use the same templates that Antlr uses (JavaScript.stg), if they meet your requirements.

Of course, if your data structure is of a nature that can be lex'd/parsed into a standard Antlr parse-tree, you can then use a standard Antlr visitor to call and populate node-specific templates.

Upvotes: 3

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