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import { Rect, Node, Txt, Line, NodeProps } from "@motion-canvas/2d";
import { createRef, all, range, makeRef, DEFAULT } from "@motion-canvas/core";
import {
CodeBlock,
insert,
edit,
lines,
} from "@motion-canvas/2d/lib/components/CodeBlock";
import { Abstraction, Application, LambdaTerm, parse } from "../parser/parser";
import {
EditOperation,
calculateLevenshteinOperations,
} from "../utils/levenshtein";
export interface LambdaReducerProps extends NodeProps {
lambdaTerm?: string;
definitions?: Record<string, string>;
}
export class LambdaReducer extends Node {
private readonly codeBlock = createRef<CodeBlock>();
private reductions: string[];
private ast: LambdaTerm;
public constructor(props?: LambdaReducerProps) {
super({
...props,
});
const functionDefinitions = props.definitions ?? {};
let lambdaTerm = props.lambdaTerm ?? "((λ x . x) (λ y . y))";
while (
Object.keys(functionDefinitions).some((x) => lambdaTerm.includes(x))
) {
lambdaTerm = Object.entries(functionDefinitions).reduce(
(acc, [name, definition]) => {
return acc.replace(new RegExp(name, "g"), definition);
},
lambdaTerm
);
}
console.log(lambdaTerm);
this.reductions = [props.lambdaTerm, lambdaTerm];
this.ast = parse(lambdaTerm);
this.add(
<CodeBlock
fontSize={25}
ref={this.codeBlock}
language="racket"
code={this.getReductions()}
></CodeBlock>
);
}
private getReductions() {
return this.reductions.filter((x) => x).join("\n=> ");
}
private isApplication(ast: any): boolean {
return ast.left && ast.right;
}
private isAbstraction(ast: any): boolean {
return ast.param && ast.body;
}
private isVariable(ast: any): boolean {
return !!ast.name;
}
private substitute(
ast: LambdaTerm,
param: string,
replacement: LambdaTerm
): LambdaTerm {
const node = ast as any;
if (this.isVariable(node)) {
return node.name === param ? replacement : node;
} else if (this.isApplication(node)) {
const left = this.substitute(node.left, param, replacement);
const right = this.substitute(node.right, param, replacement);
return { left, right } as Application;
}
return {
param: node.param,
body: this.substitute(node.body, param, replacement) as Abstraction,
};
}
public getCode() {
return this.emitCode(this.ast);
}
private betaReduceStep(ast: LambdaTerm): LambdaTerm {
const node = ast as any;
if (this.isApplication(node)) {
const left = node.left as any;
const right = node.right as any;
if (this.isAbstraction(left)) {
return this.substitute(left.body, left.param.name, right);
}
return {
left: this.betaReduceStep(left),
right: this.betaReduceStep(right),
} as Application;
}
if (this.isAbstraction(node)) {
return {
param: node.param,
body: this.betaReduceStep(node.body),
} as Abstraction;
}
return node;
}
private emitCode(ast: LambdaTerm): string {
const node = ast as any;
if (this.isVariable(node)) {
return node.name;
} else if (this.isApplication(node)) {
return `(${this.emitCode(node.left)} ${this.emitCode(node.right)})`;
} else if (this.isAbstraction(node)) {
return `(λ ${node.param.name}.${this.emitCode(node.body)})`;
}
throw new Error("Invalid lambda term");
}
public isDone() {
return (
this.emitCode(this.betaReduceStep(this.ast)) === this.emitCode(this.ast)
);
}
public *step(duration: number) {
yield* this.codeBlock().selection([], 0);
const old = this.getReductions();
const next = this.betaReduceStep(this.ast);
const nextCode = this.emitCode(next);
const operations = calculateLevenshteinOperations(
this.reductions.at(-1),
nextCode
);
yield* this.codeBlock().edit(duration)`${old}${insert(
"\n=> " + this.reductions.at(-1)
)}`;
let code = `this.codeBlock().edit(duration)\`${old}\\n=> `;
// this is SO FUCKING CURSED
window.editInLambda = edit;
window.insertInLambda = insert;
for (const { operation, diff } of operations) {
const next = `'${diff.new ?? ""}'`;
const old = `'${diff.old ?? ""}'`;
if (operation === EditOperation.Edit) {
code += `\${editInLambda(${old}, ${next})}`;
continue;
}
if (operation === EditOperation.Insert) {
code += `\${insertInLambda(${next})}`;
continue;
}
code += diff.new ?? "";
}
code += "`;";
yield* eval(code);
yield* this.codeBlock().selection(lines(this.reductions.length), 0.3);
this.reductions.push(nextCode);
this.ast = next;
}
}
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