Tree Traversal and Source Map Tools

_v1.0.0

Conflagrate bundles three common tasks when working with ASTs:

• Traversal (Walking)
• Rendering (Printing)
• Source Mapping

Node Maps

Every system within Conflagrate utilizes a map structure that details specifies the layout of nodes that a tree is comprised of. It is an object comprised of three properties:

NodeMapping

A NodeMapping provides information to Conflagrate on how to interact with a node of a given type. It can contain that type of the node, the properties of a node that should be checked for subnodes, a formatting language that defines how node should be rendered to text, and

NodeMappings

• type_name : This should be a string or a symbol that gives the property name of the node that specifier the type of the node.
• type_lookup: This is a function that returns the index of the mapping object for a given node object.
• mappings: This is an array of NodeMapping that provide

const node_mapping = {
    type_name: "type",
    type_lookup: ()=>0,
    mappings: ()=>{}

}

Tree Traversal

This all starts with defining a mappings object that is used to define the characteristics of data structures Conflagrate will encounter

//Given an AST that is comprised of these three nodes
interface Prototype  { type: string }

interface Root  extends Prototype { type:"root", expressions: EXP[]; }

interface EXP   extends Prototype { operator:string, left:EXP, right:EXP  }

interface Add   extends EXP { type:"ADD", operator:"+" }
interface Print extends EXP { type:"PRN", operator:"psh" }
interface Push  extends EXP { type:"PSH", operator:"_"  }    
interface Pop   extends EXP { type:"POP", operator:"^"  }    

type AST = Root | Add | Print | Push | Pop

//The mappings file can be made like this 
const mapping : NodeMapping = {
    typename: "type",
    type_lookup: (node, type)=>{

    },
}

Yielders

This mappings object is then used to guide the various Conflagrate utilities when operating on ASTs comprised of these nodes.

Rendering

import { render } from "@candlelib/conflagrate"

Source Maps

Source mapping is provided automatically as long line and column information is available for a node. This can be provided in the form of properties line and column that are directly on the node, or through a property object that has its own line and column properties.

Format Language Syntax:

• Member Select : @<property name>([<index number>])? - Set of

• Member Spread : @<property name>...([<any sequence of characters>])? -

• Literal : <any set of chracters> -

• Optional Newline : o:n -

• Mandatory Newline : m:n -

• Mandatory Space : m:s -

• Optional Space : o:s -

• Optional Flagged : {<property name>: rule+ } -

  Set of rules if the property the node is not undefined or null and, if its a container object, has a size or length greater than zero.

• Indent Start : i:s -

• Indent End : i:e -