simponic/the-abstraction-engine
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add max depth term

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This commit is contained in:
Elizabeth Hunt 2025-02-28 21:21:10 -07:00
parent 46afe9c7ba
commit d903bd9a13
Signed by: simponic
GPG Key ID: 2909B9A7FF6213EE
1 changed files with 23 additions and 14 deletions
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37
src/interpreter/interpreter.ts
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@ -9,6 +9,8 @@ import {
export class InvalidLambdaTermError extends Error {}
export class MaxRecursionDepthError extends Error {}
export type DebrujinAbstraction = {
abstraction: {
param: string;
@ -32,7 +34,7 @@ export type DebrujinifiedLambdaTerm =
export const debrujinify = (
term: LambdaTerm,
symbolTable: SymbolTable,
symbolTable: SymbolTable
): DebrujinifiedLambdaTerm => {
if (isVariable(term)) {
if (!symbolTable.has(term)) {
@ -65,14 +67,14 @@ export const debrujinify = (
}
throw new InvalidLambdaTermError(
`Invalid lambda term: ${JSON.stringify(term)}`,
`Invalid lambda term: ${JSON.stringify(term)}`
);
};
export const substitute = (
inTerm: DebrujinifiedLambdaTerm,
index: number,
withTerm: DebrujinifiedLambdaTerm,
withTerm: DebrujinifiedLambdaTerm
): DebrujinifiedLambdaTerm => {
if ("index" in inTerm) {
if (inTerm.index > index) {
@ -108,13 +110,13 @@ export const substitute = (
}
throw new InvalidLambdaTermError(
`Invalid lambda term: ${JSON.stringify(inTerm)}`,
`Invalid lambda term: ${JSON.stringify(inTerm)}`
);
};
export const adjustIndices = (
term: DebrujinifiedLambdaTerm,
delta: number,
delta: number
): DebrujinifiedLambdaTerm => {
if ("index" in term) {
return {
@ -146,13 +148,17 @@ export const adjustIndices = (
}
throw new InvalidLambdaTermError(
`Invalid lambda term: ${JSON.stringify(term)}`,
`Invalid lambda term: ${JSON.stringify(term)}`
);
};
export const betaReduce = (
term: DebrujinifiedLambdaTerm,
maxDepth: number,
): DebrujinifiedLambdaTerm => {
if (maxDepth === 0) {
throw new MaxRecursionDepthError("max recursion depth identified");
}
if ("index" in term) {
return term;
}
@ -162,7 +168,7 @@ export const betaReduce = (
return {
abstraction: {
body: betaReduce(body),
body: betaReduce(body, maxDepth - 1),
param,
},
};
@ -170,7 +176,9 @@ export const betaReduce = (
if ("application" in term) {
const { left } = term.application;
const args = term.application.args.map(betaReduce);
const args = term.application.args.map((term) =>
betaReduce(term, maxDepth - 1)
);
return args.reduce((acc: DebrujinifiedLambdaTerm, x) => {
if ("abstraction" in acc) {
@ -194,7 +202,7 @@ export const betaReduce = (
}
throw new InvalidLambdaTermError(
`Invalid lambda term: ${JSON.stringify(term)}`,
`Invalid lambda term: ${JSON.stringify(term)}`
);
};
@ -214,7 +222,7 @@ export const emitDebrujin = (term: DebrujinifiedLambdaTerm): string => {
}
throw new InvalidLambdaTermError(
`Invalid lambda term: ${JSON.stringify(term)}`,
`Invalid lambda term: ${JSON.stringify(term)}`
);
};
@ -225,7 +233,7 @@ export const emitNamed = (term: DebrujinifiedLambdaTerm): string => {
if ("abstraction" in term) {
return `(λ (${term.abstraction.param}) . ${emitNamed(
term.abstraction.body,
term.abstraction.body
)})`;
}
@ -241,18 +249,19 @@ export const emitNamed = (term: DebrujinifiedLambdaTerm): string => {
export const interpret = (
term: string,
symbolTable = new SymbolTable(),
allowUnderscores = false,
maxDepth = 15,
allowUnderscores = false
): DebrujinifiedLambdaTerm => {
const ast = parse(term, allowUnderscores);
const debrujined = debrujinify(ast, symbolTable);
let prev = debrujined;
let next = betaReduce(prev);
let next = betaReduce(prev, maxDepth);
while (emitDebrujin(prev) !== emitDebrujin(next)) {
// alpha equivalence
prev = next;
next = betaReduce(prev);
next = betaReduce(prev, maxDepth);
}
return next;
};