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Fix binary operator reduction & associativity handling in parser; add operator precedence tests #1

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Merged
ChasLui merged 1 commit into from
May 14, 2026
Merged

Fix binary operator reduction & associativity handling in parser; add operator precedence tests #1

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63 changes: 43 additions & 20 deletions grammar/parsing.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -51,9 +51,21 @@ interface ParserContext {
getVariable(name: string): any;
}

type OperatorAssociativity = 'left' | 'right';
interface BinaryOperatorGroup {
opSet: ReadonlySet<string>;
associativity: OperatorAssociativity;
}

class Parsing extends EmbeddedActionsParser {
private utils: Utils;
private binaryOperatorsPrecedence: string[][];
private static readonly BINARY_OPERATOR_GROUPS: ReadonlyArray<BinaryOperatorGroup> = [
{ opSet: new Set(['^']), associativity: 'right' },

@chatgpt-codex-connector chatgpt-codex-connector Bot May 14, 2026

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P2 Badge Keep exponentiation left-associative for Excel formulas

For Excel-compatible formulas, chained operators at the same precedence are evaluated left-to-right; Microsoft’s Excel precedence docs state this for same-precedence operators, so 2^3^2 should be reduced as (2^3)^2 (64), not 2^(3^2) (512). Marking ^ as right-associative changes results for any chained exponent formula and diverges from Excel behavior.

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{ opSet: new Set(['*', '/']), associativity: 'left' },
{ opSet: new Set(['+', '-']), associativity: 'left' },
{ opSet: new Set(['&']), associativity: 'left' },
{ opSet: new Set(['<', '>', '=', '<>', '<=', '>=']), associativity: 'left' },
];
private c1?: { ALT: () => string }[]; // Cache for alternatives

/**
Expand All @@ -68,13 +80,6 @@ class Parsing extends EmbeddedActionsParser {
// traceInitPerf: true,
});
this.utils = utils;
this.binaryOperatorsPrecedence = [
['^'],
['*', '/'],
['+', '-'],
['&'],
['<', '>', '=', '<>', '<=', '>='],
];
const $ = this;

// Adopted from https://github.com/spreadsheetlab/XLParser/blob/master/src/XLParser/ExcelFormulaGrammar.cs
Expand Down Expand Up @@ -105,17 +110,7 @@ class Parsing extends EmbeddedActionsParser {
values.push($.SUBRULE2(($ as any).formulaWithPercentOp));
});
$.ACTION(() => {
// evaluate
for (const ops of this.binaryOperatorsPrecedence) {
for (let index = 0, length = infixes.length; index < length; index++) {
const infix = infixes[index];
if (!ops.includes(infix)) continue;
infixes.splice(index, 1);
values.splice(index, 2, this.utils.applyInfix(values[index], infix, values[index + 1]));
index--;
length--;
}
}
this.reduceBinaryOperators(values, infixes);
});

return values[0];
Expand All @@ -128,7 +123,7 @@ class Parsing extends EmbeddedActionsParser {

($ as any).RULE('formulaWithPercentOp', () => {
let value = $.SUBRULE(($ as any).formulaWithUnaryOp);
$.OPTION(() => {
$.MANY(() => {
const postfix = $.CONSUME(PercentOp).image;
value = $.ACTION(() => this.utils.applyPostfix(value, postfix));
});
Expand Down Expand Up @@ -399,6 +394,34 @@ class Parsing extends EmbeddedActionsParser {

this.performSelfAnalysis();
}

private reduceBinaryOperators(values: any[], infixes: string[]): void {
for (const { opSet, associativity } of Parsing.BINARY_OPERATOR_GROUPS) {
if (associativity === 'right') {
// Right-associative groups, currently exponentiation, must reduce from the end.
for (let index = infixes.length - 1; index >= 0; index--) {
if (!opSet.has(infixes[index])) continue;
this.applyInfixAt(values, infixes, index);
}
continue;
}

for (let index = 0, length = infixes.length; index < length; index++) {
if (!opSet.has(infixes[index])) continue;
this.applyInfixAt(values, infixes, index);
// Re-check the same position because splicing shifts later operators left.
index--;
length--;
}
}
}

private applyInfixAt(values: any[], infixes: string[], index: number): void {
const infix = infixes[index];
infixes.splice(index, 1);
values.splice(index, 2, this.utils.applyInfix(values[index], infix, values[index + 1]));
}

}

export {
Expand Down
1 change: 1 addition & 0 deletions package.json
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Expand Up @@ -68,6 +68,7 @@
"jstat": "^1.9.6"
},
"devDependencies": {
"@types/node": "24.1.0",
"@vitest/coverage-v8": "^2.1.1",
"coveralls-next": "^5.0.0",
"docdash": "^2.0.2",
Expand Down
3 changes: 3 additions & 0 deletions pnpm-lock.yaml
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26 changes: 25 additions & 1 deletion test/operators/testcase.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -63,10 +63,34 @@ const testCases: TestCase = {
'A13+1': 1
},
'Operator Precedence': {
// '1+2*2': 5,
'1+2*2': 5,
'1+4/2+1': 4,
'1+4/2+2*3': 9,
'(1+4/2+2*3)/3^2': 1,
'2^3^2': 512,
'2^3^2^1': 512,
'2*3^2^2': 162,
'2^3*2': 16,
'(2^3)^2': 64,
'-2^2': 4,
'-(2^2)': -4,
'8/4/2': 1,
'10-3-2': 5,
'"a"&"b"&"c"': 'abc',
'"x"&1+2': 'x3',
'1+2&"x"': '3x',
'1+2=3': true,
'"a"&"b"="ab"': true,
// Chained comparisons are reduced left-to-right, not treated as mathematical ranges.
'1<2<3': false,
'3>2>1': true,
'200%^2': 4,
'200%%^2': 0.0004,
'100%%': 0.01,
'100% %': 0.01,
'5%%%': 0.000005,
'1%%%%': 0.00000001,
'(200+300)%%': 0.05,
'1-234/78+9/-78+45%': -1.6653846153846200
},
'Intersection Test': {
Expand Down
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