how can i get the height of CST

[963334657]

We have defined a set of syntax for the formula,
but I want to limit the nesting level of the formula,
how can I get the nesting level of the formula after parsing?
Do I have to calculate the height of the CST myself to get the number of nesting levels?

[msujew]

Hey @963334657,

I don't believe there's a builtin way of calculating the depth of the CST. What do you want to do in case the depth is too large? If you just throw an error it might make sense to just end parsing early in that case:

class Parser {
  depth = 0;
  SomeRule = this.Rule('rule', () => {
    this.ACTION(() => {
      if (++depth > threshold) throw new Error('too much recursion');
    });
    // ...
    this.ACTION(() => {
      depth--;
    });
  });
}

[963334657]

thank you

[bd82]

You may be able to add the depth information on the tree by overriding some methods in the treeBuilder trait,
for example:

chevrotain/packages/chevrotain/src/parse/parser/traits/tree_builder.ts

Lines 218 to 227 in 93c78cd

	cstPostNonTerminal(
	this: MixedInParser,
	ruleCstResult: CstNode,
	ruleName: string
	): void {
	const preCstNode = this.CST_STACK[this.CST_STACK.length - 1]
	addNoneTerminalToCst(preCstNode, ruleName, ruleCstResult)
	// This is only used when **both** error recovery and CST Output are enabled.
	this.setNodeLocationFromNode(preCstNode.location!, ruleCstResult.location!)
	}