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SexpVisitor.js
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SexpVisitor.js
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/**
File: SexpVisitor.js
Author: Lyn Turbak
History:
* [2020/06/18-19, lyn] Created
Return a Lisp-style s-expressionn string representation of a VenbraceForgiving parse tree.
See Sexp.js for an example.
*/
// inBrowser is defined in .html file.
// If it's defined, then we're in the browser version.
// Otherwise, we're in the terminal version = node.js version.
if ((typeof inBrowser) === 'undefined') {
inBrowser = false;
}
var antlr4;
if (inBrowser) {
antlr4 = require('./antlr4/index.js');
} else {
// antlr4 = require('antlr4');
antlr4 = require('./antlr4/index.js');
}
// var CommonToken = antlr4.CommonToken;
var VenbraceForgivingVisitor = require('./VenbraceForgivingVisitor').VenbraceForgivingVisitor;
var Utils = require('./Utils');
// ---------- Set up inheritance ----------
function SexpVisitor() {
VenbraceForgivingVisitor.call(this);
}
SexpVisitor.prototype = Object.create(VenbraceForgivingVisitor.prototype);
SexpVisitor.prototype.constructor = SexpVisitor;
// -----------------------------------------
// [2021/01/29, lyn] Modified visitTop to return the listTree rather
// than an sexpString. This makes the visitor more modular for
// use in other Venbrace contexts, such as creating an XML tree
// from the sexp listTree, which is easier than creating and XML
// tree directly via another visitor.
//
// To keep the behavior of Sexp.js the same, the call to sexpString
// has been moved there.
SexpVisitor.prototype.visitTop = function(ctx) {
var listTree = this.visitChildren(ctx);
// return sexpString(listTree);
return listTree;
}
SexpVisitor.prototype.visitTest_decl_blocks = function(ctx) {
return this.visitTop(ctx);
}
SexpVisitor.prototype.visitTest_top_blocks = function(ctx) {
return this.visitTop(ctx);
}
SexpVisitor.prototype.visitTest_blocks = function(ctx) {
return this.visitTop(ctx);
}
SexpVisitor.prototype.visitTest_program = function(ctx) {
return this.visitTop(ctx);
}
SexpVisitor.prototype.visitProgram = function(ctx) {
return this.visitTop(ctx);
}
SexpVisitor.prototype.visitChildren = function(ctx) {
var nameWithContext = Utils.className(ctx);
var nameWithoutContext = nameWithContext.split('Context')[0].toLowerCase();
if (ctx.children) {
// ctx.children is a list (i.e., JavaScript array)
var sublist = ctx.children.map ( child => child.accept(this) ).filter( elt => ! tokensToOmit.includes(elt) );
var listKeyword = listKeywordMap[nameWithoutContext];
if (listKeyword) {
sublist.unshift(listKeyword);
} else if (sublist.length === 1) {
return sublist[0]; // Simple wrapper; just keep contents
} else {
// console.log('Unshifting ' + nameWithoutContext + ' for length ' + sublist.length);
sublist.unshift(nameWithoutContext);
}
if ((sublist[0] === 'seq') && (sublist.length === 2)) {
return sublist[1]; // Simplify seq with one element
} else if (sublist[0] === 'mod') {
var newSublist = sublist.filter ( elt => elt !== '/' );
return newSublist;
} else if (sublist[0] === 'subnegnumexpr') {
sublist[2] = Math.abs(sublist[2]); // position of negative number
sublist[0] = '-';
return sublist;
} else if (sublist[0].startsWith('proc')) {
// collect param names in parens
var lastIndex = sublist.length-1;
var procName = sublist[1];
var params = sublist.slice(2,lastIndex);
var body = sublist[lastIndex];
return [sublist[0], procName, params, body];
} else if (sublist[0] === 'if_stat') {
if (sublist.length <= 4) { // if/then or if/then/else
sublist.shift();
sublist.unshift('if'); // replace if_stat by if
return sublist;
} else {
var lastIndex= sublist.length - 1;
var tests = sublist.filter ( (elt, index) => (index % 2 == 1 && index < lastIndex) );
var thens = sublist.filter ( (elt, index) => (index % 2 == 0 && index > 0) );
var lastElse = sublist.length % 2 == 1 ? undefined : sublist[lastIndex];
var newSublist = ['cond', Utils.zip(tests, thens)]
if (lastElse) {
newSublist.push(['else', lastElse]);
}
return newSublist;
}
} else {
var operators = operatorMap[sublist[0]];
if (operators) {
var op = operators.find( s => (sublist.includes(s) ));
newSublist = sublist.filter ( elt => elt !== op );
newSublist[0] = op;
return newSublist;
} else {
return sublist;
}
}
} else {
console.log('Returning null for ctx ' + nameWithoutContext);
return null;
}
}
var braces = ['[', ']', '{', '}' , '(', ')'];
var tokensToOmit =
braces.concat(
['top', 'decl', 'stat', 'expr',
'to', 'do', 'result', 'when',
'if', 'then', 'else', 'else if',
'for each', 'test', 'from', 'by', 'in', 'call', 'set',
'not', 'modulo', 'of',
'length', 'join', 'reverse', 'split at spaces'
]);
var listKeywordMap = {
'test_top_blocks': 'blocks',
'test_blocks': 'blocks',
'test_program': 'block',
'program': 'decls',
'suite': 'seq',
'event_handler': 'when',
'for_each_from_to': 'forEach',
'immutable_neg_num_special_case': '-',
'setter': 'set',
'not_expr': 'not',
'procedure_do': 'procNoReturn',
'procedure_result': 'procReturn',
'str_length': 'length',
'str_join': 'join',
'str_reverse': 'reverse',
'str_split_at_spaces': 'split_at_spaces',
}
var operatorMap = {
'andexpr': ['and'],
'orexpr': ['or'],
'mutablemulexpr': ['*'],
'mutableaddexpr': ['+'],
'subexpr': ['-'],
'divexpr': ['/'],
'powexpr': ['^'],
'mathcompareexpr': ['<', '<=', '=', '!=', '>=', '>'],
'mutable_op': ['+', '*'],
'immutable_regular_case': ['-', '/', '^'],
'compare_math_expr': ['<', '<=', '=', '!=', '>=', '>'],
'logic_expr': ['and', 'or'],
'min_max' : ['min', 'max'],
'unary_op' : ['square root', 'absolute', 'neg', 'log', 'e^', 'round', 'ceiling', 'floor'],
'trig': ['sin', 'cos', 'tan', 'asin', 'acos', 'atan']
}
// Not used yet
var indentAfterKeywordMap = {
'topBlocks': 0,
'when': 1,
'initLocal': 1,
'initGlobal': 1,
'forEach': 4
}
SexpVisitor.prototype.visitGlobal_decl = function(ctx) {
return ['initGlobal', toToken(ctx.ID()).text, this.visit(ctx.suite())];
}
SexpVisitor.prototype.visitLocal_var_decl_stat = function(ctx) {
var bindings = [];
var i = 0;
var id = ctx.ID(i);
while (id) {
bindings.push([toToken(id).text, this.visit(ctx.expr_block(i))]);
i++;
var id = ctx.ID(i);
}
return ['initLocal', bindings, this.visit(ctx.suite())];
}
SexpVisitor.prototype.visitTerminal = function(ctx) {
// Default handler for terminal tokens not handled by explicit visitor
var token = ctx.getSymbol(); // Returns the token at the terminal
var text = token.text;
// console.log('visitTerminal ' + text);
// var parentNameWithContext = ctx.getParent().constructor.name;
// if (isBrace(text)) {
// console.log('Brace token ' + text + ' with parent ' + parentNameWithContext);
//
// if (isOptional(ctx, token)) {
// token['optional'] = true;
// }
return text;
};
function toToken(ctxOrToken) {
// extract a token from ctxOrToken, or propagate null/undefined
// Lyn sez Can't use instanceof with TerminalNodeImpl because I can't
// figure out how to import TerminalNodeImpl
if (ctxOrToken == null) {
return null;
}
if (ctxOrToken == undefined) {
return undefined;
}
var className = Utils.className(ctxOrToken);
// console.log('toToken className: ' + className);
if (className === "LbraceContext" || className === "RbraceContext") {
return ctxOrToken.start;
} else if (className === "TerminalNodeImpl") {
return ctxOrToken.getSymbol();
} else if (className === "CommonToken") {
return ctxOrToken;
} else {
throw "can't convert object to a token: " + className;
}
}
function sexpString(listTree) {
function sexpStrings(ltr, width) {
if (['string', 'number'].includes(typeof ltr)) {
return [ltr];
} else if (! (ltr instanceof Array)) {
throw 'sexpString expected Array but found ' + (typeof ltr)
+ ': ' + ltr.toString();
return [ltr];
} else { // must be array
if ((ltr.length === 0) || ((ltr[0] === 'core_expr') && ltr.length === 1)) {
// list is empty
return ['()'];
} else {
// list has at least one element
// might begin with keyword or be list of name/sexp bindings
var keyword = ltr[0];
if ((typeof keyword) !== 'string') {
keyword = undefined;
}
var prefix = '(' + (keyword ? keyword + ' ' : '');
var indent = prefix.length;
var subwidth = width - indent;
var subStringss = ltr.map( lt => sexpStrings(lt, subwidth) );
var sexp = oneLineSexp(subStringss);
if (sexp && sexp.length <= width) {
return [sexp];
}
var outStrings;
if (keyword) {
if (subStringss.length === 1) {
return [prefix + ')'];
} else {
subStringss[0].shift(); // remove keyword, leaving stringss[0] empty
outStrings = [prefix + subStringss[1].shift()]; // remove first string from stringss[1]
// and add it on same line with keyword
}
} else {
outStrings = [prefix + subStringss[0].shift()]; // remove first string from stringss[0]
}
subStringss.forEach(
function (strings) {
strings.forEach( function(str) {
outStrings.push(Utils.spaces(indent) + str)
});
});
var lastIndex = outStrings.length - 1;
outStrings[lastIndex] += ')'; // Close paren to match open paren in index
return outStrings;
}
}
}
function oneLineSexp(eltsStringss) {
// If each list of strings has length 1, concatenate the singletons
// in each list wrapped in parens. Else return undefined
if (eltsStringss.every( eltStrings => eltStrings.length === 1)) {
return '(' + eltsStringss.map( eltStrings => eltStrings[0] ).join(' ') + ')';
} else {
return undefined;
}
}
// Return a single string with newlines between lines
// console.log('List tree input to sexpString:');
// console.log(listTree);
return sexpStrings(listTree, 100).join('\n');
}
// [2021/01/29, lyn] "export" sexpString as a functionality of an sexp visitor
SexpVisitor.prototype.sexpString = sexpString;
exports.SexpVisitor = SexpVisitor;