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const std = @import("std");
const tok = @import("tokenize.zig");
const SyntaxError = error{SyntaxError};
const expectedToken = error{ExpectedToken};
pub const BinOp = enum(u32) {
Add = 0b000,
Sub = 0b001,
Mul = 0b100,
Div = 0b101,
Mod = 0b110,
fn init(typ: tok.TokenType) ?BinOp {
return switch (typ) {
.plus => .Add,
.minus => .Sub,
.star => .Mul,
.slash => .Div,
else => null,
};
}
fn greater(self: BinOp, other: ?BinOp) bool {
if (other == null) return true;
return (@intFromEnum(self) >> 2) > (@intFromEnum(other.?) >> 2);
}
};
pub const Literal = union(enum) {
Int: i32,
};
pub const AstExpr = struct {
kind: ExprKind,
allocator: std.mem.Allocator,
pub fn init(allocator: std.mem.Allocator) !*AstExpr {
const value = try allocator.create(AstExpr);
value.* = .{
.kind = .Void,
.allocator = allocator,
};
return value;
}
pub fn deinit(self: *AstExpr) void {
self.allocator.free(self);
}
};
pub const AstStmt = struct {
kind: StmtKind,
allocator: std.mem.Allocator,
pub fn init(allocator: std.mem.Allocator) !*AstStmt {
const value = try allocator.create(AstStmt);
value.* = .{
.kind = .Void,
.allocator = allocator,
};
return value;
}
pub fn deinit(self: *AstStmt) void {
self.allocator.free(self);
}
};
pub const Ast = union(enum) {
Expr: AstExpr,
Stmt: AstStmt,
};
const StmtKind = union(enum) {
exit: AstExpr,
Void,
};
const ExprKind = union(enum) {
Literal: Literal,
BinaryOp: struct {
op: BinOp,
left: *AstExpr,
right: *AstExpr,
},
Void,
};
const AstParser = struct {
tokens: tok.Iterator(tok.Token),
arena: std.heap.ArenaAllocator,
allocator: std.mem.Allocator,
fn init(allocator: *std.heap.ArenaAllocator, tokens: tok.Iterator(tok.Token)) AstParser {
return AstParser{
.tokens = tokens,
.arena = allocator.*,
.allocator = allocator.allocator(),
};
}
fn deinit(self: *AstParser) void {
self.arena.deinit();
}
fn parseStmt(self: *AstParser) !AstStmt {
return switch (self.tokens.peek().?) {
.ret => self.exitStmt(),
else => error.SyntaxError,
};
}
fn parseExpr(self: *AstParser, lastOp: ?BinOp) !*AstExpr {
if (!tok.checkType(self.tokens.peek().?, tok.TokenType.intLit)) return error.ExpectedToken;
const kind = ExprKind{ .Literal = .{ .Int = self.tokens.consume().?.intLit } };
var lhs = try AstExpr.init(self.allocator);
lhs.*.kind = kind;
while (self.tokens.peek()) |tokn| {
const op = BinOp.init(tokn);
if (op != null and op.?.greater(lastOp)) {
self.tokens.skip();
const rhs = try self.parseExpr(op);
const newkind = ExprKind{ .BinaryOp = .{
.op = op.?,
.left = lhs,
.right = rhs,
} };
lhs = try AstExpr.init(self.allocator);
lhs.*.kind = newkind;
}
return lhs;
}
return lhs;
}
fn exitStmt(self: *AstParser) !AstStmt {
if (!tok.checkType(self.tokens.consume().?, tok.TokenType.ret))
return error.ExpectedToken;
const value = try self.parseExpr(null);
if (!tok.checkType(self.tokens.consume().?, tok.TokenType.semiCol)) return error.ExpectedToken;
const kind = StmtKind{ .exit = value.* };
const stmt = try AstStmt.init(self.allocator);
stmt.kind = kind;
return stmt.*;
}
};
test "AstParse" {
std.testing.log_level = std.log.Level.info;
const expect = std.testing.expect;
const testSource: []const u8 = "exit 120 + 150;";
var toks = tok.Tokenizer.init(std.testing.allocator, testSource);
defer toks.deinit();
var arrtoks = try toks.tokenize();
const slice = try arrtoks.toOwnedSlice();
const iter = tok.Iterator(tok.Token).init(slice);
var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
var parser = AstParser.init(&arena, iter);
defer parser.deinit();
const stmt = try parser.parseStmt();
_ = stmt;
_ = expect;
}
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