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Parsing bindings. adding AST pretty printer

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Dustin Swan 2026-02-01 00:43:01 -07:00
parent 1fc116f2fe
commit 0f0371461d
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GPG key ID: 30D46587E2100467
4 changed files with 64 additions and 42 deletions
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64
src/parser.ts
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@ -22,6 +22,14 @@ export class Parser {
return this.tokens[this.pos++];
}
private peek(offset = 1): Token {
const pos = this.pos + offset;
if (pos >= this.tokens.length) {
return { kind: 'eof' } as Token;
}
return this.tokens[pos];
}
private expect(kind: Token['kind']): Token {
const token = this.current();
@ -65,9 +73,24 @@ export class Parser {
}
private parseExpression(): AST {
if (this.current().kind === 'ident' && this.peek().kind === 'equals') {
return this.parseLet();
}
return this.parseInfix();
}
private parseLet(): AST {
const nameToken = this.expect('ident');
const name = (nameToken as { value: string }).value;
this.expect('equals');
const value = this.parseInfix();
this.expect('semicolon');
const body = this.parseExpression();
return { kind: 'let', name, value, body };
}
private parseInfix(): AST {
let left = this.parseApplication();
@ -177,47 +200,6 @@ export class Parser {
}
/*
private parseMultiplicative(): AST {
let left = this.parsePostfix();
while (this.current().kind === 'star' || this.current().kind === 'slash') {
const op = this.current().kind === 'star' ? '*' : '/';
this.advance();
const right = this.parsePostfix();
left = { kind: 'binaryop', operator: op, left, right };
}
return left;
}
private parseAdditive(): AST {
let left = this.parseMultiplicative();
while (this.current().kind === 'plus' || this.current().kind === 'minus') {
const op = this.current().kind === 'plus' ? '+' : '-';
this.advance();
const right = this.parseMultiplicative();
left = { kind: 'binaryop', operator: op, left, right };
}
return left;
}
private parseLet(): AST {
this.expect('let');
const nameToken = this.expect('ident');
const name = (nameToken as { value: string }).value;
this.expect('equals');
const value = this.parseExpression();
this.expect('in');
const body = this.parseExpression();
return { kind: 'let', name, value, body };
}
private parseLambda(): AST {
this.expect('open-paren');