parser

jest.config.js

@@ -1,5 +1,5 @@
 /** @type {import('ts-jest').JestConfigWithTsJest} */
 module.exports = {
-  preset: 'ts-jest',
+  preset: "ts-jest",
-  testEnvironment: 'node',
+  testEnvironment: "node",
 };

src/ast.ts

@@ -1,33 +1,116 @@
 import { Span } from "./error";
 
 export type ItemKind = {
-    kind: "function",
+  kind: "function";
-    node: FunctionDef,
+  node: FunctionDef;
 };
 
 export type Item = ItemKind & {
-    span: Span,
+  span: Span;
-}
+};
 
 export type FunctionDef = {
-    name: string,
+  name: string;
-    args: FunctionArg[], 
+  args: FunctionArg[];
-    body: Expr,
+  body: Expr;
-}
+};
 
 export type FunctionArg = {
-    name: string,
+  name: string;
-    span: Span,
+  span: Span;
-}
+};
 
-export type ExprKind = {
+export type ExprKind =
-    kind: "lit_string",
+  | { kind: "empty" }
-    value: string,
+  | { kind: "let"; name: string; rhs: Expr; after: Expr }
-} | {
+  | { kind: "block"; exprs: Expr[] }
-    kind: "ident",
+  | {
-    value: string,
+      kind: "literal";
-}
+      value: Literal;
+    }
+  | {
+      kind: "ident";
+      value: string;
+    }
+  | {
+      kind: "binary";
+      binaryKind: BinaryKind;
+      lhs: Expr;
+      rhs: Expr;
+    }
+  | {
+    kind: "unary",
+    unaryKind: UnaryKind,
+    rhs: Expr,
+  }
+  | {
+    kind: "call",
+    lhs: Expr,
+    args: Expr[],
+  };
 
 export type Expr = ExprKind & {
-    span: Span,
+  span: Span;
+};
+
+export type Literal =
+  | {
+      kind: "str";
+      value: string;
+    }
+  | {
+      kind: "int";
+      value: number;
+    };
+
+export type BinaryKind =
+  | "+"
+  | "-"
+  | "*"
+  | "/"
+  | "&"
+  | "|"
+  | "<"
+  | ">"
+  | "=="
+  | "<="
+  | ">="
+  | "!=";
+
+export const COMPARISON_KINDS: BinaryKind[] = [
+  ">",
+  "<",
+  "==",
+  "<=",
+  ">=",
+  "!=",
+];
+export const LOGICAL_KINDS: BinaryKind[] = ["&", "|"];
+export const ARITH_TERM_KINDS: BinaryKind[] = ["+", "-"];
+export const ARITH_FACTOR_KINDS: BinaryKind[] = ["*", "/"];
+
+const BINARY_KIND_PREC_CLASS = new Map<BinaryKind, number>([
+  ["+", 0],
+  ["-", 0],
+  ["*", 0],
+  ["/", 0],
+  ["&", 1],
+  ["|", 2],
+  ["<", 3],
+  [">", 4],
+  ["==", 5],
+  ["<=", 6],
+  [">=", 7],
+  ["!=", 8],
+]);
+
+export function binaryExprPrecedenceClass(k: BinaryKind): number {
+  const cls = BINARY_KIND_PREC_CLASS.get(k);
+  if (!cls) {
+    throw new Error(`Invalid binary kind: ${k}`);
+  }
+  return cls;
 }
+
+export type UnaryKind = '!' | '-';
+export const UNARY_KINDS: UnaryKind[] = ['!', '-'];

src/error.ts

@@ -3,6 +3,13 @@ export type Span = {
   end: number;
 };
 
+export function spanMerge(a: Span, b: Span): Span {
+  return {
+    start: Math.min(a.start, b.start),
+    end: Math.max(a.end, b.end),
+  };
+}
+
 export class CompilerError extends Error {
   msg: string;
   span: Span;

src/index.ts

@@ -1,18 +1,30 @@
 import { withErrorHandler } from "./error";
 import { tokenize } from "./lexer";
 import { parse } from "./parser";
+import { printAst } from "./printer";
 
 const input = `
-function hello() {}
+function main() = (
+  print("Hello, world!");
+  "uwu";
+);
 `;
 
 function main() {
   withErrorHandler(input, () => {
     const tokens = tokenize(input);
+    console.log("-----TOKENS---");
     console.log(tokens);
 
     const ast = parse(tokens);
-    console.log(ast);
+    console.log("-----AST------");
+    
+    console.dir(ast, { depth: 10 });
+
+    const printed = printAst(ast);
+    console.log("-----AST pretty------");
+    console.log(printed);
+    
   });
 }
 

src/lexer.test.ts

@@ -1,17 +1,17 @@
 import { tokenize } from "./lexer";
 
-it('should tokenize an emtpy function', () => {
+it("should tokenize an emtpy function", () => {
-    const input = `function hello() {}`;
+  const input = `function hello() = {}`;
 
-    const tokens = tokenize(input);
+  const tokens = tokenize(input);
 
-    expect(tokens).toMatchSnapshot();
+  expect(tokens).toMatchSnapshot();
 });
 
-it('should tokenize hello world', () => {
+it("should tokenize hello world", () => {
-    const input = `print("hello world")`;
+  const input = `print("hello world")`;
 
-    const tokens = tokenize(input);
+  const tokens = tokenize(input);
 
-    expect(tokens).toMatchSnapshot();
+  expect(tokens).toMatchSnapshot();
 });

src/lexer.ts

@@ -1,23 +1,62 @@
 import { CompilerError, Span } from "./error";
 
 export type DatalessToken =
-  | "kw_function"
+  | "function"
-  | "kw_let"
+  | "let"
-  | "p_popen"
+  | "in"
-  | "p_pclose"
+  | "("
-  | "p_bopen"
+  | ")"
-  | "p_bclose"
+  | ";"
-  | "p_semi";
+  | ","
+  | "="
+  | "+"
+  | "-"
+  | "*"
+  | "/"
+  | "&"
+  | "|"
+  | "!"
+  | "<"
+  | ">"
+  | "=="
+  | "<="
+  | ">="
+  | "!="
+  | "!";
 
-export type TokenKind =
+export type TokenIdent = { kind: "identifier"; ident: string };
-  | { kind: DatalessToken }
+
-  | { kind: "identifier"; ident: string }
+export type TokenLit =
-  | { kind: "lit_string"; value: string };
+  | {
+      kind: "lit_string";
+      value: string;
+    }
+  | {
+      kind: "lit_int";
+      value: number;
+    };
+
+export type TokenKind = { kind: DatalessToken } | TokenIdent | TokenLit;
 
 export type Token = TokenKind & {
   span: Span;
 };
 
+export type BaseToken = { kind: Token["kind"] };
+
+const SINGLE_PUNCT: string[] = [
+  "(",
+  ")",
+  ";",
+  ",",
+  "+",
+  "-",
+  "*",
+  "/",
+  "&",
+  "|",
+];
+
 export function tokenize(input: string): Token[] {
   const tokens: Token[] = [];
   let i = 0;
@@ -25,65 +64,102 @@ export function tokenize(input: string): Token[] {
   finish: while (i < input.length) {
     const next = input[i];
     const span: Span = { start: i, end: i + 1 };
-    switch (next) {
+
-      case undefined: {
+    if (SINGLE_PUNCT.includes(next)) {
-        break finish;
+      tokens.push({ kind: next as DatalessToken, span });
-      }
+    } else {
-      case "(": {
+      switch (next) {
-        tokens.push({ kind: "p_popen", span });
+        case undefined: {
-        break;
+          break finish;
-      }
-      case ")": {
-        tokens.push({ kind: "p_pclose", span });
-        break;
-      }
-      case "{": {
-        tokens.push({ kind: "p_bopen", span });
-        break;
-      }
-      case "}": {
-        tokens.push({ kind: "p_bclose", span });
-        break;
-      }
-      case ";": {
-        tokens.push({ kind: "p_semi", span });
-        break;
-      }
-      case '"': {
-        while (true) {
-          const next = input[i + 1];
-          span.end++;
-          i++;
-          if (next === '"') {
-            break;
-          }
-          if (next === undefined) {
-            throw new CompilerError(`Unterminated string literal`, span);
-          }
         }
-        const value = input.slice(span.start + 1, span.end - 1);
+        case "=": {
-        tokens.push({ kind: "lit_string", span, value });
+          if (input[i + 1] === "=") {
-        break;
-      }
-      default: {
-        if (isDigit(next)) {
-          throw new Error("digit");
-        } else if (isIdentStart(next)) {
-          while (isIdentContinue(input[i + 1])) {
             span.end++;
             i++;
-          }
+            tokens.push({ kind: "==", span });
-          const ident = input.slice(span.start, span.end);
-          let kw = isKeyword(ident);
-          if (kw) {
-            tokens.push({ kind: kw, span });
           } else {
-            tokens.push({ kind: "identifier", span, ident: ident });
+            tokens.push({ kind: "=", span });
+          }
+          break;
+        }
+        case ">": {
+          if (input[i + 1] === "=") {
+            span.end++;
+            i++;
+            tokens.push({ kind: ">=", span });
+          } else {
+            tokens.push({ kind: ">", span });
+          }
+          break;
+        }
+        case "<": {
+          if (input[i + 1] === "=") {
+            span.end++;
+            i++;
+            tokens.push({ kind: "<=", span });
+          } else {
+            tokens.push({ kind: "<", span });
+          }
+          break;
+        }
+        case "!": {
+          if (input[i + 1] === "=") {
+            span.end++;
+            i++;
+            tokens.push({ kind: "!=", span });
+          } else {
+            tokens.push({ kind: "!", span });
+          }
+          break;
+        }
+        case '"': {
+          while (true) {
+            const next = input[i + 1];
+            span.end++;
+            i++;
+            if (next === '"') {
+              break;
+            }
+            if (next === undefined) {
+              throw new CompilerError(`Unterminated string literal`, span);
+            }
+          }
+          const value = input.slice(span.start + 1, span.end - 1);
+          tokens.push({ kind: "lit_string", span, value });
+          break;
+        }
+        default: {
+          if (isDigit(next)) {
+            while (isDigit(input[i + 1])) {
+              span.end++;
+              i++;
+            }
+            const digit = input.slice(span.start, span.end);
+            const int = parseInt(digit, 10);
+            if (Number.isNaN(int)) {
+              throw new Error(
+                `\`${digit}\` was tokenized to a number even though it is not`
+              );
+            }
+
+            tokens.push({ kind: "lit_int", value: int, span });
+          } else if (isIdentStart(next)) {
+            while (isIdentContinue(input[i + 1])) {
+              span.end++;
+              i++;
+            }
+            const ident = input.slice(span.start, span.end);
+            let kw = isKeyword(ident);
+            if (kw) {
+              tokens.push({ kind: kw, span });
+            } else {
+              tokens.push({ kind: "identifier", span, ident: ident });
+            }
+          } else if (isWhitespace(next)) {
+            // ignore
+          } else {
+            throw new CompilerError(`Invalid character: \`${next}\``, span);
           }
-        } else if (isWhitespace(next)) {
-          // ignore
-        } else {
-          throw new CompilerError(`Invalid character: \`${next}\``, span);
         }
       }
     }
@@ -117,10 +193,7 @@ function isWhitespace(char: string): boolean {
   return char === " " || char === "\t" || char === "\n" || char === "\r";
 }
 
-const keywords = new Map<string, DatalessToken>([
+const keywords = new Set<string>(["function", "let", "in"]);
-  ["function", "kw_function"],
-  ["let", "kw_let"],
-]);
 function isKeyword(kw: string): DatalessToken | undefined {
-  return keywords.get(kw);
+  return keywords.has(kw) ? (kw as DatalessToken) : undefined;
 }

src/parser.ts

@@ -1,45 +1,282 @@
-import { FunctionDef, Item } from "./ast";
+import {
+  ARITH_FACTOR_KINDS,
+  ARITH_TERM_KINDS,
+  BinaryKind,
+  COMPARISON_KINDS,
+  Expr,
+  FunctionDef,
+  Item,
+  LOGICAL_KINDS,
+  UNARY_KINDS,
+  UnaryKind,
+} from "./ast";
 import { CompilerError, todo } from "./error";
-import { Token } from "./lexer";
+import { BaseToken, Token, TokenIdent } from "./lexer";
+
+type Parser<T> = (t: Token[]) => [Token[], T];
 
 export function parse(t: Token[]): Item[] {
-    const items: Item[] = [];
+  const items: Item[] = [];
 
-    while (t.length > 0) {
+  while (t.length > 0) {
-        let item;
+    let item;
-        [t, item] = parseItem(t);
+    [t, item] = parseItem(t);
-        items.push(item);
+    items.push(item);
-    }
+  }
 
-    return items;
+  return items;
 }
 
 function parseItem(t: Token[]): [Token[], Item] {
-    let next;
+  let tok;
-    [t, next] = nextT(t);
+  [t, tok] = next(t);
-    if (next.kind === "kw_function") {
+  if (tok.kind === "function") {
+    let name;
+    [t, name] = expectNext<TokenIdent>(t, "identifier");
 
-        const def: FunctionDef = {
+    [t] = expectNext(t, "(");
-            name: "",
+    [t] = expectNext(t, ")");
-            args: [],
+    [t] = expectNext(t, "=");
-            body: todo("todo", next.span)
-        }
 
-        return [t, {kind: "function", node: def, span: next.span}]
+    let body;
-    } else {
+    [t, body] = parseExpr(t);
-        unexpectedToken(next);
+
-    }
+    [t] = expectNext(t, ";");
+
+    const def: FunctionDef = {
+      name: name.ident,
+      args: [],
+      body,
+    };
+
+    return [t, { kind: "function", node: def, span: tok.span }];
+  } else {
+    unexpectedToken(tok);
+  }
 }
 
-function nextT(t: Token[]): [Token[], Token] {
+function parseExpr(t: Token[]): [Token[], Expr] {
-    const next = t[0];
+  /*
-    if (!next) {
+  EXPR = { "let" NAME "=" EXPR "in" EXPR | COMPARISON }
-        throw new CompilerError("unexpected end of file", {start: Number.MAX_SAFE_INTEGER, end: Number.MAX_SAFE_INTEGER})
+
+  // The precende here is pretty arbitrary since we forbid mixing of operators
+  // with different precedence classes anyways.
+  COMPARISON = LOGICAL { ( ">" | "<" | "==" | "<=" | ">=" | "!=" ) COMPARISON }
+  LOGICAL = ARITH_TERM { ( "&" | "|" ) LOGICAL }
+
+  // Here it matters though.
+  ARITH_TERM = ATOM { ( "+" | "-" ) ARITH_TERM }
+  ARITH_FACTOR = UNARY { ( "*" | "/" ) ARITH_FACTOR }
+
+  UNARY = { "!" | "-" } CALL
+
+  CALL = ATOM { "(" EXPR_LIST ")" }
+
+  ATOM = "(" { EXPR ";" } EXPR ")" | IDENT | LITERAL | EMPTY
+  EMPTY =
+  EXPR_LIST = { EXPR { "," EXPR } { "," } }
+  */
+  const [, peak] = next(t);
+
+  if (peak.kind === "let") {
+    [t] = next(t);
+    let name;
+    [t, name] = expectNext<TokenIdent>(t, "identifier");
+    expectNext(t, "=");
+    let rhs;
+    [t, rhs] = parseExpr(t);
+    expectNext(t, "in");
+    let after;
+    [t, after] = parseExpr(t);
+
+    return [t, { kind: "let", name: name.ident, rhs, after, span: t[0].span }];
+  }
+
+  return parseExprComparison(t);
+}
+
+function mkParserExprBinary(
+  lower: Parser<Expr>,
+  kinds: string[]
+): Parser<Expr> {
+  function parser(t: Token[]): [Token[], Expr] {
+    let lhs;
+    [t, lhs] = lower(t);
+
+    const [, peak] = next(t);
+    if (kinds.includes(peak.kind)) {
+      [t] = next(t);
+      let rhs;
+      [t, rhs] = parser(t);
+      const span = peak.span;
+      return [
+        t,
+        { kind: "binary", binaryKind: peak.kind as BinaryKind, lhs, rhs, span },
+      ];
     }
-    const rest = t.slice(1);
+
-    return [rest, next];
+    return [t, lhs];
+  }
+
+  return parser;
+}
+
+const parseExprArithFactor = mkParserExprBinary(
+  parseExprUnary,
+  ARITH_FACTOR_KINDS
+);
+
+const parseExprArithTerm = mkParserExprBinary(
+  parseExprArithFactor,
+  ARITH_TERM_KINDS
+);
+
+const parseExprLogical = mkParserExprBinary(parseExprArithTerm, LOGICAL_KINDS);
+
+const parseExprComparison = mkParserExprBinary(
+  parseExprLogical,
+  COMPARISON_KINDS
+);
+
+function parseExprUnary(t: Token[]): [Token[], Expr] {
+  const [, peak] = next(t);
+  if (peak.kind in UNARY_KINDS) {
+    let rhs;
+    [t, rhs] = parseExprUnary(t);
+    return [
+      t,
+      {
+        kind: "unary",
+        unaryKind: peak.kind as UnaryKind,
+        rhs,
+        span: peak.span,
+      },
+    ];
+  }
+
+  return parseExprCall(t);
+}
+function parseExprCall(t: Token[]): [Token[], Expr] {
+  let lhs: Expr;
+  [t, lhs] = parseExprAtom(t);
+
+  while (next(t)[1].kind === "(") {
+    let popen;
+    [t, popen] = next(t);
+    const args = [];
+    while (next(t)[1].kind !== ")") {
+      let arg;
+      [t, arg] = parseExpr(t);
+      args.push(arg);
+      // TODO i think this is incorrect
+      [t] = eat(t, ",");
+    }
+    [t] = expectNext(t, ")");
+
+    lhs = { kind: "call", span: popen.span, lhs, args };
+  }
+
+  return [t, lhs];
+}
+
+function parseExprAtom(startT: Token[]): [Token[], Expr] {
+  let [t, tok] = next(startT);
+
+  if (tok.kind === "(") {
+    let expr: Expr;
+    [t, expr] = parseExpr(t);
+
+    const exprs = [expr];
+    while (next(t)[1].kind !== ")") {
+      [t] = expectNext(t, ";");
+      [t, expr] = parseExpr(t);
+      exprs.push(expr);
+    }
+    [t] = expectNext(t, ")");
+
+    return [t, { kind: "block", span: tok.span, exprs }];
+  }
+
+  if (tok.kind === "lit_string") {
+    return [
+      t,
+      {
+        kind: "literal",
+        span: tok.span,
+        value: { kind: "str", value: tok.value },
+      },
+    ];
+  }
+
+  if (tok.kind === "lit_int") {
+    return [
+      t,
+      {
+        kind: "literal",
+        span: tok.span,
+        value: { kind: "int", value: tok.value },
+      },
+    ];
+  }
+
+  if (tok.kind === "identifier") {
+    return [t, { kind: "ident", span: tok.span, value: tok.ident }];
+  }
+
+  // Parse nothing at all.
+  return [startT, { kind: "empty", span: tok.span }];
+}
+
+// helpers
+
+function eat<T extends BaseToken>(
+  t: Token[],
+  kind: T["kind"]
+): [Token[], T | undefined] {
+  const [tnext, tok] = next(t);
+  if (tok.kind === kind) {
+    return [tnext, tok as unknown as T];
+  }
+  return [t, undefined];
+}
+
+function expectNext<T extends BaseToken>(
+  t: Token[],
+  kind: T["kind"]
+): [Token[], T] {
+  let tok;
+  [t, tok] = next(t);
+  const token = expectToken(kind, tok);
+  return [t, token];
+}
+
+function next(t: Token[]): [Token[], Token] {
+  const [rest, next] = maybeNextT(t);
+  if (!next) {
+    throw new CompilerError("unexpected end of file", {
+      start: Number.MAX_SAFE_INTEGER,
+      end: Number.MAX_SAFE_INTEGER,
+    });
+  }
+  return [rest, next];
+}
+
+function maybeNextT(t: Token[]): [Token[], Token | undefined] {
+  const next = t[0];
+  const rest = t.slice(1);
+  return [rest, next];
 }
 
 function unexpectedToken(token: Token): never {
-    throw new CompilerError("unexpected token", token.span);
+  throw new CompilerError("unexpected token", token.span);
+}
+
+function expectToken<T extends BaseToken>(kind: T["kind"], token: Token): T {
+  if (token.kind !== kind) {
+    throw new CompilerError(
+      `expected ${kind}, found ${token.kind}`,
+      token.span
+    );
+  }
+  return token as unknown as T;
 }

src/printer.ts

@@ -0,0 +1,96 @@
+import { Expr, FunctionDef, Item } from "./ast";
+
+export function printAst(ast: Item[]): string {
+  return ast.map(printItem).join("\n");
+}
+
+function printItem(item: Item): string {
+  switch (item.kind) {
+    case "function": {
+      return printFunction(item.node);
+    }
+  }
+}
+
+function printFunction(func: FunctionDef): string {
+  const args = func.args.map(({ name }) => name).join(", ");
+  return `function ${func.name}(${args}) = ${printExpr(func.body, 0)}`;
+}
+
+function printExpr(expr: Expr, indent: number): string {
+  switch (expr.kind) {
+    case "empty": {
+      return "";
+    }
+    case "let": {
+      return `let ${expr.name} = ${printExpr(expr.rhs, 1)} in${linebreak(
+        indent
+      )}`;
+    }
+    case "block": {
+      const exprs = expr.exprs.map((expr) => printExpr(expr, indent + 1));
+
+      if (exprs.length === 1) {
+        return `(${exprs[0]})`;
+      }
+      const shortExprs =
+        exprs.map((s) => s.length).reduce((a, b) => a + b, 0) < 40;
+      if (shortExprs) {
+        const alreadyHasTrailingSpace = expr.exprs[exprs.length - 1]?.kind === "empty";
+        const trailingSpace = alreadyHasTrailingSpace ? "" : " ";
+        return `( ${exprs.join("; ")}${trailingSpace})`;
+      } else {
+        const joiner = `;${linebreak(indent + 1)}`;
+        return (
+          `(${linebreak(indent + 1)}` +
+          `${exprs.join(joiner)}` +
+          `${linebreak(indent)})`
+        );
+      }
+    }
+    case "literal": {
+      switch (expr.value.kind) {
+        case "str": {
+          return `"${expr.value.value}"`;
+        }
+        case "int": {
+          return `${expr.value.value}`;
+        }
+      }
+    }
+    case "ident": {
+      return expr.value;
+    }
+    case "binary": {
+      return `${printExpr(expr.lhs, indent)} ${expr.binaryKind} ${printExpr(
+        expr.rhs,
+        indent
+      )}`;
+    }
+    case "unary": {
+      return `${expr.unaryKind}${printExpr(expr.rhs, indent)}`;
+    }
+    case "call": {
+      const args = expr.args.map((arg) => printExpr(arg, indent + 1));
+      const shortArgs =
+        args.map((s) => s.length).reduce((a, b) => a + b, 0) < 40;
+      if (shortArgs) {
+        return `${printExpr(expr.lhs, indent)}(${args.join(", ")})`;
+      } else {
+        return (
+          `${printExpr(expr.lhs, indent)}(${linebreak(indent + 1)}` +
+          `${args.join(linebreak(indent + 1))}` +
+          `${linebreak(indent)})`
+        );
+      }
+    }
+  }
+}
+
+function linebreak(indent: number): string {
+  return `\n${ind(indent)}`;
+}
+
+function ind(indent: number): string {
+  return "  ".repeat(indent * 2);
+}

tsconfig.json

@@ -95,7 +95,7 @@
     // "noUnusedParameters": true,                       /* Raise an error when a function parameter isn't read. */
     // "exactOptionalPropertyTypes": true,               /* Interpret optional property types as written, rather than adding 'undefined'. */
     // "noImplicitReturns": true,                        /* Enable error reporting for codepaths that do not explicitly return in a function. */
-    "noFallthroughCasesInSwitch": true,                  /* Enable error reporting for fallthrough cases in switch statements. */
+    "noFallthroughCasesInSwitch": true /* Enable error reporting for fallthrough cases in switch statements. */,
     // "noUncheckedIndexedAccess": true,                 /* Add 'undefined' to a type when accessed using an index. */
     // "noImplicitOverride": true,                       /* Ensure overriding members in derived classes are marked with an override modifier. */
     // "noPropertyAccessFromIndexSignature": true,       /* Enforces using indexed accessors for keys declared using an indexed type. */