commit b2b1533ee61660d5936303432fc83a5078680527
Author: SimonFJ20 <simonfromjakobsen@gmail.com>
Date:   Thu Apr 27 02:32:06 2023 +0200

    init

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..882c025
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+session.vim
diff --git a/checked.ts b/checked.ts
new file mode 100644
index 0000000..6904c7c
--- /dev/null
+++ b/checked.ts
@@ -0,0 +1,99 @@
+import { AssignType, BinaryType, UnaryType } from "./parsed.ts";
+import { Position } from "./token.ts";
+
+export type CheckedExpr =
+    & {
+        pos: Position;
+    }
+    & ({ exprType: "error"; message: string } | {
+        exprType: "unit";
+    } | {
+        exprType: "id";
+        value: string;
+    } | {
+        exprType: "int";
+        value: number;
+    } | {
+        exprType: "if";
+        condition: CheckedExpr;
+        truthy: CheckedExpr;
+        falsy: CheckedExpr | null;
+    } | {
+        exprType: "block";
+        body: CheckedExpr[];
+    } | {
+        exprType: "call";
+        subject: CheckedExpr;
+        args: CheckedExpr[];
+    } | {
+        exprType: "index";
+        subject: CheckedExpr;
+        value: CheckedExpr;
+    } | {
+        exprType: "increment" | "decrement";
+        subject: CheckedExpr;
+    } | {
+        exprType: "unary";
+        unaryType: UnaryType;
+        subject: CheckedExpr;
+    } | {
+        exprType: "binary";
+        binaryType: BinaryType;
+        left: CheckedExpr;
+        right: CheckedExpr;
+    } | {
+        exprType: "assign";
+        assignType: AssignType;
+        subject: CheckedExpr;
+        value: CheckedExpr;
+    } | {
+        exprType: "let";
+        param: CheckedParameter;
+        value: CheckedExpr;
+    } | {
+        exprType: "fn";
+        subject: string;
+        params: CheckedParameter[];
+        body: CheckedExpr;
+    } | {
+        exprType: "return";
+        value: CheckedExpr | null;
+    } | {
+        exprType: "loop";
+        body: CheckedExpr;
+    } | {
+        exprType: "while";
+        condition: CheckedExpr;
+        body: CheckedExpr;
+    } | {
+        exprType: "break";
+    } | {
+        exprType: "continue";
+    });
+
+export type CheckedParameter =
+    & {
+        pos: Position;
+    }
+    & ({ paramType: "error"; message: string } | {
+        paramType: "value";
+        subject: string;
+        valueType: CheckedType | null;
+        mutable: boolean;
+    });
+
+export type CheckedType =
+    & { pos: Position }
+    & ({ typeType: "error"; message: string } | {
+        typeType: "unit";
+    } | {
+        typeType: "u16";
+    } | {
+        typeType: "pointer";
+        subject: CheckedType;
+        mutable: boolean;
+    } | {
+        typeType: "function";
+        params: CheckedParameter[];
+        returnType: CheckedType;
+    });
diff --git a/checker.ts b/checker.ts
new file mode 100644
index 0000000..8c1c402
--- /dev/null
+++ b/checker.ts
@@ -0,0 +1,55 @@
+import { CheckedExpr, CheckedType } from "./checked.ts";
+import { ParsedExpr } from "./parsed.ts";
+import { CompileError } from "./token.ts";
+
+export type SymbolValue = {
+    id: number;
+    subject: string;
+    valueType: CheckedType;
+};
+
+export class SymbolTable {
+    private idCounter = 0;
+    private symbols: { [key: string]: SymbolValue } = {};
+
+    public define(subject: string, valueType: CheckedType) {
+        if (subject in this.symbols) {
+            throw new Error("redefinition not implemented");
+        }
+        const id = this.idCounter;
+        this.idCounter++;
+        this.symbols[subject] = { id, subject, valueType };
+    }
+}
+
+export class Checker {
+    private symbolTable = new SymbolTable();
+    public errors: CompileError[] = [];
+
+    public check(statements: ParsedExpr[]): CheckedExpr[] {
+        return statements as CheckedExpr[];
+    }
+
+    private searchTopLevelStatements(statements: ParsedExpr[]) {
+        for (const statement of statements) {
+            switch (statement.exprType) {
+                case "fn":
+                    this.searchTopLevelFn(statement);
+                    break;
+                case "let":
+                    break;
+                default:
+                    this.errors.push({
+                        pos: statement.pos,
+                        message:
+                            `statement '${statement.exprType}' not supported in top level`,
+                    });
+                    break;
+            }
+        }
+    }
+
+    private searchTopLevelFn(statement: ParsedExpr & { exprType: "fn" }) {
+    }
+}
+
diff --git a/deno.jsonc b/deno.jsonc
new file mode 100644
index 0000000..ae1f70d
--- /dev/null
+++ b/deno.jsonc
@@ -0,0 +1,10 @@
+{
+    "fmt": {
+        "options": {
+          "useTabs":false,
+          "lineWidth": 80,
+          "indentWidth": 4,
+          "singleQuote": false
+        }
+    }
+}
diff --git a/lexer.ts b/lexer.ts
new file mode 100644
index 0000000..c424b2e
--- /dev/null
+++ b/lexer.ts
@@ -0,0 +1,218 @@
+import { Position, StaticTokenType, Token, TokenIter } from "./token.ts";
+
+export class Lexer implements TokenIter {
+    private index = 0;
+    private line = 1;
+    private col = 1;
+
+    public constructor(private text: string) {}
+
+    public next(): Token {
+        if (this.done()) {
+            return { pos: this.position(), tokenType: "eof" };
+        } else if (" \t\r\n".includes(this.current())) {
+            this.step();
+            while (" \t\r\n".includes(this.current())) this.step();
+            return this.next();
+        } else if (Lexer.idStartChars.includes(this.current())) {
+            const pos = this.position();
+            let valueString = this.current();
+            this.step();
+            while (Lexer.idChars.includes(this.current())) {
+                valueString += this.current();
+                this.step();
+            }
+            if (valueString in Lexer.keywordTokenTypes) {
+                return { pos, tokenType: Lexer.keywordTokenTypes[valueString] };
+            } else {
+                return {
+                    pos,
+                    tokenType: "id",
+                    value: valueString,
+                };
+            }
+        } else if (Lexer.intStartChars.includes(this.current())) {
+            const pos = this.position();
+            let valueString = this.current();
+            this.step();
+            while (Lexer.intChars.includes(this.current())) {
+                valueString += this.current();
+                this.step();
+            }
+            return {
+                pos,
+                tokenType: "int",
+                value: parseInt(valueString),
+            };
+        } else if (this.current() in Lexer.singleStaticTokenTypes) {
+            const pos = this.position();
+            const tokenType = Lexer.singleStaticTokenTypes[this.current()];
+            this.step();
+            return { pos, tokenType };
+        } else if (this.currentIs("+")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("+")) {
+                this.step();
+                return { pos, tokenType: "plusplus" };
+            } else if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "plusequal" };
+            } else {
+                return { pos, tokenType: "plus" };
+            }
+        } else if (this.currentIs("-")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("-")) {
+                this.step();
+                return { pos, tokenType: "minusminus" };
+            } else if (this.currentIs(">")) {
+                this.step();
+                return { pos, tokenType: "minusgt" };
+            } else if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "minusequal" };
+            } else {
+                return { pos, tokenType: "minus" };
+            }
+        } else if (this.currentIs("&")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "ampersandequal" };
+            } else {
+                return { pos, tokenType: "ampersand" };
+            }
+        } else if (this.currentIs("|")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "pipeequal" };
+            } else {
+                return { pos, tokenType: "pipe" };
+            }
+        } else if (this.currentIs("^")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "hatequal" };
+            } else {
+                return { pos, tokenType: "hat" };
+            }
+        } else if (this.currentIs("=")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "equalequal" };
+            } else {
+                return { pos, tokenType: "equal" };
+            }
+        } else if (this.currentIs("!")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "exclamationequal" };
+            } else {
+                return { pos, tokenType: "exclamation" };
+            }
+        } else if (this.currentIs("<")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "ltequal" };
+            } else {
+                return { pos, tokenType: "lt" };
+            }
+        } else if (this.currentIs(">")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("=")) {
+                this.step();
+                return { pos, tokenType: "gtequal" };
+            } else {
+                return { pos, tokenType: "gt" };
+            }
+        } else {
+            const pos = this.position();
+            this.step();
+            return { pos, tokenType: "invalid" };
+        }
+    }
+
+    private static intStartChars = "123456789" as const;
+    private static intChars = "1234567890" as const;
+    private static idStartChars =
+        "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_" as const;
+    private static idChars = Lexer.idStartChars + Lexer.intChars;
+
+    private static singleStaticTokenTypes: { [key: string]: StaticTokenType } =
+        {
+            "(": "lparen",
+            ")": "rparen",
+            "{": "lbrace",
+            "}": "rbrace",
+            "[": "lbracket",
+            "]": "rbracket",
+            ".": "dot",
+            ",": "comma",
+            ":": "colon",
+            ";": "semicolon",
+            "~": "tilde",
+            "*": "asterisk",
+        } as const;
+
+    private static keywordTokenTypes: { [key: string]: StaticTokenType } = {
+        "let": "let",
+        "mut": "mut",
+        "not": "not",
+        "and": "and",
+        "or": "or",
+        "fn": "fn",
+        "return": "return",
+        "if": "fn",
+        "else": "else",
+        "loop": "loop",
+        "while": "while",
+        "break": "break",
+        "continue": "continue",
+    } as const;
+
+    private step() {
+        this.index++;
+        if (!this.done()) {
+            if (this.current() == "\n") {
+                this.line++;
+                this.col = 1;
+            } else {
+                this.col++;
+            }
+        }
+    }
+
+    private position(): Position {
+        return {
+            index: this.index,
+            line: this.line,
+            col: this.col,
+        };
+    }
+
+    private currentIs(char: string): boolean {
+        return !this.done() && this.current() == char;
+    }
+
+    private current(): string {
+        return this.text[this.index];
+    }
+
+    private done(): boolean {
+        return this.index >= this.text.length;
+    }
+}
diff --git a/main.ts b/main.ts
new file mode 100644
index 0000000..91ed071
--- /dev/null
+++ b/main.ts
@@ -0,0 +1,10 @@
+async function readFromStdin() {
+    const buffer = new Uint8Array(8192);
+    const n = await Deno.stdin.read(buffer);
+    return new TextDecoder().decode(buffer.subarray(0, n!));
+}
+
+async function main() {
+}
+
+main();
diff --git a/parsed.ts b/parsed.ts
new file mode 100644
index 0000000..de3c711
--- /dev/null
+++ b/parsed.ts
@@ -0,0 +1,126 @@
+import { Position } from "./token.ts";
+
+export type UnaryType =
+    | "negate"
+    | "log_not"
+    | "bit_not"
+    | "addressof"
+    | "dereference";
+
+export type BinaryType =
+    | "add"
+    | "subtract"
+    | "log_and"
+    | "log_or"
+    | "bit_and"
+    | "bit_or"
+    | "bit_xor"
+    | "equal"
+    | "inequal"
+    | "lt"
+    | "gt"
+    | "ltequal"
+    | "gtequal";
+
+export type AssignType =
+    | "equal"
+    | "add"
+    | "subtract"
+    | "and"
+    | "or"
+    | "xor";
+
+export type ParsedExpr =
+    & {
+        pos: Position;
+    }
+    & ({ exprType: "error"; message: string } | {
+        exprType: "unit";
+    } | {
+        exprType: "id";
+        value: string;
+    } | {
+        exprType: "int";
+        value: number;
+    } | {
+        exprType: "if";
+        condition: ParsedExpr;
+        truthy: ParsedExpr;
+        falsy: ParsedExpr | null;
+    } | {
+        exprType: "block";
+        body: ParsedExpr[];
+    } | {
+        exprType: "call";
+        subject: ParsedExpr;
+        args: ParsedExpr[];
+    } | {
+        exprType: "index";
+        subject: ParsedExpr;
+        value: ParsedExpr;
+    } | {
+        exprType: "increment" | "decrement";
+        subject: ParsedExpr;
+    } | {
+        exprType: "unary";
+        unaryType: UnaryType;
+        subject: ParsedExpr;
+    } | {
+        exprType: "binary";
+        binaryType: BinaryType;
+        left: ParsedExpr;
+        right: ParsedExpr;
+    } | {
+        exprType: "assign";
+        assignType: AssignType;
+        subject: ParsedExpr;
+        value: ParsedExpr;
+    } | {
+        exprType: "let";
+        param: ParsedParameter;
+        value: ParsedExpr;
+    } | {
+        exprType: "fn";
+        subject: string;
+        params: ParsedParameter[];
+        returnType: ParsedType | null;
+        body: ParsedExpr;
+    } | {
+        exprType: "return";
+        value: ParsedExpr | null;
+    } | {
+        exprType: "loop";
+        body: ParsedExpr;
+    } | {
+        exprType: "while";
+        condition: ParsedExpr;
+        body: ParsedExpr;
+    } | {
+        exprType: "break";
+    } | {
+        exprType: "continue";
+    });
+
+export type ParsedParameter =
+    & {
+        pos: Position;
+    }
+    & ({ paramType: "error"; message: string } | {
+        paramType: "value";
+        subject: string;
+        valueType: ParsedType | null;
+        mutable: boolean;
+    });
+
+export type ParsedType =
+    & { pos: Position }
+    & ({ typeType: "error"; message: string } | {
+        typeType: "unit";
+    } | {
+        typeType: "id";
+        value: string;
+    } | {
+        typeType: "pointer";
+        subject: ParsedType;
+        mutable: boolean;
+    });
diff --git a/parser.ts b/parser.ts
new file mode 100644
index 0000000..67001c6
--- /dev/null
+++ b/parser.ts
@@ -0,0 +1,758 @@
+import {
+    BinaryType,
+    ParsedExpr,
+    ParsedParameter,
+    ParsedType,
+} from "./parsed.ts";
+import {
+    CompileError,
+    Position,
+    Token,
+    TokenIter,
+    TokenType,
+} from "./token.ts";
+
+export class Parser {
+    private current: Token;
+    public errors: CompileError[] = [];
+
+    public constructor(private lexer: TokenIter) {
+        this.current = lexer.next();
+    }
+
+    public parse(): ParsedExpr[] {
+        while (this.currentIs("semicolon")) this.step();
+        const statements: ParsedExpr[] = [];
+        while (!this.done()) {
+            while (this.currentIs("semicolon")) this.step();
+        }
+        return statements;
+    }
+
+    private checkAndSkipStatementLinebreak() {
+        if (!this.currentIs("semicolon")) {
+            this.errors.push({
+                pos: this.position(),
+                message:
+                    `expected ';' after statement, got '${this.current.tokenType}'`,
+            });
+        } else {
+            this.step();
+        }
+    }
+
+    public parseStatement(): ParsedExpr {
+        if (this.currentIs("fn")) {
+            return this.parseFn();
+        } else if (this.currentIs("if")) {
+            return this.parseIf();
+        } else if (this.currentIs("loop")) {
+            return this.parseLoop();
+        } else if (this.currentIs("while")) {
+            return this.parseWhile();
+        } else if (this.currentIs("return")) {
+            const statement = this.parseReturn();
+            this.checkAndSkipStatementLinebreak();
+            return statement;
+        } else if (this.currentIs("break")) {
+            const statement = this.parseBreak();
+            this.checkAndSkipStatementLinebreak();
+            return statement;
+        } else if (this.currentIs("continue")) {
+            const statement = this.parseContinue();
+            this.checkAndSkipStatementLinebreak();
+            return statement;
+        } else if (this.currentIs("let")) {
+            const statement = this.parseLet();
+            this.checkAndSkipStatementLinebreak();
+            return statement;
+        } else {
+            const statement = this.parseAssign();
+            this.checkAndSkipStatementLinebreak();
+            return statement;
+        }
+    }
+
+    private parseFn(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        if (this.done() || this.current.tokenType != "id") {
+            return this.errorExpr(
+                `expected 'Id' after 'fn' as function name, got '${this.current.tokenType}'`,
+            );
+        }
+        const subject = this.current.value;
+        this.step();
+        if (!this.currentIs("lparen")) {
+            return this.errorExpr(
+                `expected '(' before function-parameters, got '${this.current.tokenType}'`,
+            );
+        }
+        this.step();
+        const params: ParsedParameter[] = [];
+        params.push(this.parseParam());
+        while (this.currentIs("comma")) {
+            this.step();
+            if (this.done() || this.currentIs("rparen")) break;
+            params.push(this.parseParam());
+        }
+        if (!this.currentIs("rparen")) {
+            return this.errorExpr(
+                `expected ')' after function-parameters, got '${this.current.tokenType}'`,
+            );
+        }
+        this.step();
+        let returnType: ParsedType | null = null;
+        if (this.currentIs("minusgt")) {
+            this.step();
+            returnType = this.parseType();
+        }
+        if (!this.currentIs("lbrace")) {
+            return this.errorExpr(
+                `expected '{' after 'loop', got '${this.current.tokenType}'`,
+            );
+        }
+        const body = this.parseBlock();
+        return {
+            pos,
+            exprType: "fn",
+            subject,
+            params,
+            returnType,
+            body,
+        };
+    }
+
+    private parseLoop(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        if (!this.currentIs("lbrace")) {
+            return this.errorExpr(
+                `expected '{' after 'loop', got '${this.current.tokenType}'`,
+            );
+        }
+        const body = this.parseBlock();
+        return {
+            pos,
+            exprType: "loop",
+            body,
+        };
+    }
+
+    private parseWhile(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        const condition = this.parseExpr();
+        if (!this.currentIs("lbrace")) {
+            return this.errorExpr(
+                `expected '{' after while-condition, got '${this.current.tokenType}'`,
+            );
+        }
+        const body = this.parseBlock();
+        return {
+            pos,
+            exprType: "while",
+            condition,
+            body,
+        };
+    }
+
+    private parseReturn(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        let value: ParsedExpr | null = null;
+        if (!this.done() && this.current.tokenType != "semicolon") {
+            value = this.parseExpr();
+        }
+        return { pos, exprType: "return", value };
+    }
+
+    private parseBreak(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        return { pos, exprType: "break" };
+    }
+
+    private parseContinue(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        return { pos, exprType: "continue" };
+    }
+
+    private parseLet(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        const param = this.parseParam();
+        if (!this.currentIs("equal")) {
+            return this.errorExpr(
+                `expected '=' after let-parameter, got '${this.current.tokenType}'`,
+            );
+        }
+        this.step();
+        const value = this.parseExpr();
+        return {
+            pos,
+            exprType: "let",
+            param,
+            value,
+        };
+    }
+
+    private parseParam(): ParsedParameter {
+        const pos = this.position();
+        const mutable = this.currentIs("mut");
+        if (mutable) this.step();
+        if (this.done() || this.current.tokenType != "id") {
+            return this.errorParam(
+                `expected 'id' in parameter, got '${this.current.tokenType}'`,
+            );
+        }
+        const subject = this.current.value;
+        this.step();
+        let valueType: ParsedType | null = null;
+        if (this.currentIs("colon")) {
+            this.step();
+            valueType = this.parseType();
+        }
+        return {
+            pos,
+            paramType: "value",
+            subject,
+            valueType,
+            mutable,
+        };
+    }
+
+    private parseAssign(): ParsedExpr {
+        const pos = this.position();
+        const subject = this.parseExpr();
+        if (this.currentIs("equal")) {
+            this.step();
+            const value = this.parseExpr();
+            return {
+                pos,
+                exprType: "assign",
+                assignType: "equal",
+                subject,
+                value,
+            };
+        } else if (this.currentIs("plusequal")) {
+            this.step();
+            const value = this.parseExpr();
+            return {
+                pos,
+                exprType: "assign",
+                assignType: "add",
+                subject,
+                value,
+            };
+        } else if (this.currentIs("minusequal")) {
+            this.step();
+            const value = this.parseExpr();
+            return {
+                pos,
+                exprType: "assign",
+                assignType: "subtract",
+                subject,
+                value,
+            };
+        } else if (this.currentIs("ampersandequal")) {
+            this.step();
+            const value = this.parseExpr();
+            return {
+                pos,
+                exprType: "assign",
+                assignType: "and",
+                subject,
+                value,
+            };
+        } else if (this.currentIs("pipeequal")) {
+            this.step();
+            const value = this.parseExpr();
+            return {
+                pos,
+                exprType: "assign",
+                assignType: "or",
+                subject,
+                value,
+            };
+        } else if (this.currentIs("hatequal")) {
+            this.step();
+            const value = this.parseExpr();
+            return {
+                pos,
+                exprType: "assign",
+                assignType: "xor",
+                subject,
+                value,
+            };
+        } else {
+            return subject;
+        }
+    }
+
+    public parseExpr(): ParsedExpr {
+        return this.parseLogOr();
+    }
+
+    private binaryExpr(
+        binaryType: BinaryType,
+        left: ParsedExpr,
+        right: ParsedExpr,
+        pos: Position,
+    ): ParsedExpr {
+        return {
+            pos,
+            exprType: "binary",
+            binaryType,
+            left,
+            right,
+        };
+    }
+
+    private parseLogOr(): ParsedExpr {
+        const pos = this.position();
+        let left = this.parseLogAnd();
+        while (!this.done()) {
+            if (this.currentIs("or")) {
+                this.step();
+                const right = this.parseLogAnd();
+                left = this.binaryExpr("log_or", left, right, pos);
+            } else {
+                break;
+            }
+        }
+        return left;
+    }
+
+    private parseLogAnd(): ParsedExpr {
+        const pos = this.position();
+        let left = this.parseBitOr();
+        while (!this.done()) {
+            if (this.currentIs("and")) {
+                this.step();
+                const right = this.parseBitOr();
+                left = this.binaryExpr("log_and", left, right, pos);
+            } else {
+                break;
+            }
+        }
+        return left;
+    }
+
+    private parseBitOr(): ParsedExpr {
+        const pos = this.position();
+        let left = this.parseBitXor();
+        while (!this.done()) {
+            if (this.currentIs("pipe")) {
+                this.step();
+                const right = this.parseBitXor();
+                left = this.binaryExpr("bit_or", left, right, pos);
+            } else {
+                break;
+            }
+        }
+        return left;
+    }
+
+    private parseBitXor(): ParsedExpr {
+        const pos = this.position();
+        let left = this.parseBitAnd();
+        while (!this.done()) {
+            if (this.currentIs("hat")) {
+                this.step();
+                const right = this.parseBitAnd();
+                left = this.binaryExpr("bit_xor", left, right, pos);
+            } else {
+                break;
+            }
+        }
+        return left;
+    }
+
+    private parseBitAnd(): ParsedExpr {
+        const pos = this.position();
+        let left = this.parseEquality();
+        while (!this.done()) {
+            if (this.currentIs("ampersand")) {
+                this.step();
+                const right = this.parseEquality();
+                left = this.binaryExpr("bit_and", left, right, pos);
+            } else {
+                break;
+            }
+        }
+        return left;
+    }
+
+    private parseEquality(): ParsedExpr {
+        const pos = this.position();
+        let left = this.parseComparison();
+        while (!this.done()) {
+            if (this.currentIs("equalequal")) {
+                this.step();
+                const right = this.parseComparison();
+                left = this.binaryExpr("equal", left, right, pos);
+            } else if (this.currentIs("exclamationequal")) {
+                this.step();
+                const right = this.parseComparison();
+                left = this.binaryExpr("inequal", left, right, pos);
+            } else {
+                break;
+            }
+        }
+        return left;
+    }
+
+    private parseComparison(): ParsedExpr {
+        const pos = this.position();
+        const left = this.parseAddSubtract();
+        if (this.currentIs("lt")) {
+            this.step();
+            const right = this.parseAddSubtract();
+            return this.binaryExpr("lt", left, right, pos);
+        } else if (this.currentIs("gt")) {
+            this.step();
+            const right = this.parseAddSubtract();
+            return this.binaryExpr("gt", left, right, pos);
+        } else if (this.currentIs("ltequal")) {
+            this.step();
+            const right = this.parseAddSubtract();
+            return this.binaryExpr("ltequal", left, right, pos);
+        } else if (this.currentIs("gtequal")) {
+            this.step();
+            const right = this.parseAddSubtract();
+            return this.binaryExpr("gtequal", left, right, pos);
+        } else {
+            return left;
+        }
+    }
+
+    private parseAddSubtract(): ParsedExpr {
+        const pos = this.position();
+        let left = this.parseUnary();
+        while (!this.done()) {
+            if (this.currentIs("plus")) {
+                this.step();
+                const right = this.parseUnary();
+                left = this.binaryExpr("add", left, right, pos);
+            } else if (this.currentIs("minus")) {
+                this.step();
+                const right = this.parseUnary();
+                left = this.binaryExpr("subtract", left, right, pos);
+            } else {
+                break;
+            }
+        }
+        return left;
+    }
+
+    private parseUnary(): ParsedExpr {
+        if (this.currentIs("minus")) {
+            const pos = this.position();
+            this.step();
+            return {
+                pos,
+                exprType: "unary",
+                unaryType: "negate",
+                subject: this.parseUnary(),
+            };
+        } else if (this.currentIs("not")) {
+            const pos = this.position();
+            this.step();
+            return {
+                pos,
+                exprType: "unary",
+                unaryType: "log_not",
+                subject: this.parseUnary(),
+            };
+        } else if (this.currentIs("tilde")) {
+            const pos = this.position();
+            this.step();
+            return {
+                pos,
+                exprType: "unary",
+                unaryType: "bit_not",
+                subject: this.parseUnary(),
+            };
+        } else if (this.currentIs("ampersand")) {
+            const pos = this.position();
+            this.step();
+            return {
+                pos,
+                exprType: "unary",
+                unaryType: "addressof",
+                subject: this.parseUnary(),
+            };
+        } else if (this.currentIs("asterisk")) {
+            const pos = this.position();
+            this.step();
+            return {
+                pos,
+                exprType: "unary",
+                unaryType: "dereference",
+                subject: this.parseUnary(),
+            };
+        } else {
+            return this.parseCallIndex();
+        }
+    }
+
+    private parseCallIndex(): ParsedExpr {
+        const pos = this.position();
+        let subject = this.parseOperand();
+        while (!this.done()) {
+            if (this.currentIs("lparen")) {
+                this.step();
+                const args: ParsedExpr[] = [];
+                if (!this.done() && this.current.tokenType != "rparen") {
+                    args.push(this.parseExpr());
+                    while (this.currentIs("comma")) {
+                        this.step();
+                        if (this.done() || this.currentIs("rparen")) {
+                            break;
+                        }
+                        args.push(this.parseExpr());
+                    }
+                }
+                if (!this.currentIs("rparen")) {
+                    return this.errorExpr(
+                        `expected ')', got '${this.current.tokenType}'`,
+                    );
+                }
+                this.step();
+                subject = {
+                    pos,
+                    exprType: "call",
+                    subject,
+                    args,
+                };
+            } else if (this.currentIs("lbracket")) {
+                this.step();
+                const value = this.parseExpr();
+                if (!this.currentIs("rbracket")) {
+                    return this.errorExpr(
+                        `expected ']', got '${this.current.tokenType}'`,
+                    );
+                }
+                this.step();
+                subject = {
+                    pos,
+                    exprType: "index",
+                    subject,
+                    value,
+                };
+            } else {
+                break;
+            }
+        }
+        return subject;
+    }
+
+    private parseOperand(): ParsedExpr {
+        if (this.current.tokenType == "id") {
+            const pos = this.position();
+            const value = this.current.value;
+            this.step();
+            return {
+                pos,
+                exprType: "id",
+                value,
+            };
+        } else if (this.current.tokenType == "int") {
+            const pos = this.position();
+            const value = this.current.value;
+            this.step();
+            return {
+                pos,
+                exprType: "int",
+                value,
+            };
+        } else if (this.currentIs("lparen")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("rparen")) {
+                this.step();
+                return { pos, exprType: "unit" };
+            }
+            const subject = this.parseExpr();
+            if (!this.currentIs("rparen")) {
+                return this.errorExpr(
+                    `expected ')', got '${this.current.tokenType}'`,
+                );
+            }
+            this.step();
+            subject.pos = pos;
+            return subject;
+        } else if (this.currentIs("if")) {
+            return this.parseIf();
+        } else if (this.currentIs("lbrace")) {
+            return this.parseBlock();
+        } else {
+            return this.errorExpr(
+                `expected operand, got '${this.current.tokenType}'`,
+            );
+        }
+    }
+
+    private parseIf(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        const condition = this.parseExpr();
+        if (!this.currentIs("lbrace")) {
+            return this.errorExpr(
+                `expected '{' after if-condition, got '${this.current.tokenType}'`,
+            );
+        }
+        const truthy = this.parseBlock();
+        let falsy: ParsedExpr | null = null;
+        if (this.currentIs("else")) {
+            this.step();
+            if (!this.currentIs("lbrace")) {
+                return this.errorExpr(
+                    `expected '{' after 'else', got '${this.current.tokenType}'`,
+                );
+            }
+            falsy = this.parseBlock();
+        }
+        return {
+            pos,
+            exprType: "if",
+            condition,
+            truthy,
+            falsy,
+        };
+    }
+
+    private parseBlock(): ParsedExpr {
+        const pos = this.position();
+        this.step();
+        while (this.currentIs("semicolon")) this.step();
+        const body: ParsedExpr[] = [];
+        while (!this.done() && this.current.tokenType != "rbrace") {
+            body.push(this.parseStatement());
+            while (this.currentIs("semicolon")) this.step();
+        }
+        if (!this.currentIs("rbrace")) {
+            return this.errorExpr(
+                `expected '}' after block, got '${this.current.tokenType}'`,
+            );
+        }
+        this.step();
+        return {
+            pos,
+            exprType: "block",
+            body,
+        };
+    }
+
+    private parseType(): ParsedType {
+        return this.parsePointerType();
+    }
+
+    private parsePointerType(): ParsedType {
+        if (this.currentIs("asterisk")) {
+            const pos = this.position();
+            this.step();
+            let mutable = false;
+            if (this.currentIs("mut")) {
+                mutable = true;
+                this.step();
+            }
+            const subject = this.parseTypeOperand();
+            return {
+                pos,
+                typeType: "pointer",
+                subject,
+                mutable,
+            };
+        } else {
+            return this.parseTypeOperand();
+        }
+    }
+
+    private parseTypeOperand(): ParsedType {
+        if (this.current.tokenType == "id") {
+            const pos = this.position();
+            const value = this.current.value;
+            this.step();
+            return {
+                pos,
+                typeType: "id",
+                value,
+            };
+        } else if (this.currentIs("lparen")) {
+            const pos = this.position();
+            this.step();
+            if (this.currentIs("rparen")) {
+                this.step();
+                return { pos, typeType: "unit" };
+            }
+            const subject = this.parseType();
+            if (!this.currentIs("rparen")) {
+                return this.errorType(
+                    `expected ')', got '${this.current.tokenType}'`,
+                );
+            }
+            this.step();
+            subject.pos = pos;
+            return subject;
+        } else {
+            return this.errorType(
+                `expected type, got '${this.current.tokenType}'`,
+            );
+        }
+    }
+
+    private errorExpr(
+        message: string,
+        pos: Position = this.position(),
+    ): ParsedExpr {
+        this.errors.push({ pos, message });
+        return {
+            pos,
+            exprType: "error",
+            message,
+        };
+    }
+
+    private errorParam(
+        message: string,
+        pos: Position = this.position(),
+    ): ParsedParameter {
+        this.errors.push({ pos, message });
+        return {
+            pos,
+            paramType: "error",
+            message,
+        };
+    }
+
+    private errorType(
+        message: string,
+        pos: Position = this.position(),
+    ): ParsedType {
+        this.errors.push({ pos, message });
+        return {
+            pos,
+            typeType: "error",
+            message,
+        };
+    }
+
+    private position() {
+        return this.current.pos;
+    }
+
+    private step() {
+        this.current = this.lexer.next();
+    }
+
+    private currentIs(tokenType: TokenType): boolean {
+        return this.current.tokenType == tokenType;
+    }
+
+    private done(): boolean {
+        return this.current.tokenType == "eof";
+    }
+}
diff --git a/token.ts b/token.ts
new file mode 100644
index 0000000..d33e0ca
--- /dev/null
+++ b/token.ts
@@ -0,0 +1,76 @@
+export type Position = { index: number; line: number; col: number };
+
+export type CompileError = { pos: Position; message: string };
+
+export type DynamicTokenType = "id" | "int";
+
+export type StaticTokenType =
+    | "eof"
+    | "invalid"
+    | "lparen"
+    | "rparen"
+    | "lbrace"
+    | "rbrace"
+    | "lbracket"
+    | "rbracket"
+    | "dot"
+    | "comma"
+    | "colon"
+    | "semicolon"
+    | "plus"
+    | "plusplus"
+    | "plusequal"
+    | "minus"
+    | "minusminus"
+    | "minusequal"
+    | "minusgt"
+    | "asterisk"
+    | "tilde"
+    | "ampersand"
+    | "ampersandequal"
+    | "pipe"
+    | "pipeequal"
+    | "hat"
+    | "hatequal"
+    | "equal"
+    | "equalequal"
+    | "exclamation"
+    | "exclamationequal"
+    | "lt"
+    | "gt"
+    | "ltequal"
+    | "gtequal"
+    | "not"
+    | "and"
+    | "or"
+    | "let"
+    | "mut"
+    | "fn"
+    | "return"
+    | "if"
+    | "else"
+    | "loop"
+    | "while"
+    | "break"
+    | "continue";
+
+export type TokenType = DynamicTokenType | StaticTokenType;
+
+export type Token =
+    & {
+        pos: Position;
+    }
+    & (
+        | { tokenType: "id"; value: string }
+        | {
+            tokenType: "int";
+            value: number;
+        }
+        | {
+            tokenType: StaticTokenType;
+        }
+    );
+
+export interface TokenIter {
+    next(): Token;
+}