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|
const std = @import("std");
const tok = @import("tokenize.zig");
const Iterator = tok.Iterator;
const Token = tok.Token;
const ParsingError = error{
InvalidExpression,
ExpectedExit,
ExpectedSemicolon,
ExpectedEqual,
ExpectedIdentifier,
InvalidStatement,
};
pub const NodeExpr = union(enum) {
intLit: NodeIntlit,
ident: NodeIdent,
};
pub const NodeStmt = union(enum) {
exit: NodeExit,
value: NodeValue,
assign: NodeAssign,
};
pub const NodeAssign = struct {
ident: Token,
value: NodeExpr,
};
pub const NodeValue = struct {
ident: Token,
value: NodeExpr,
isConst: bool,
};
pub const NodeExit = struct {
expr: NodeExpr,
};
pub const NodeIntlit = struct {
intlit: Token,
};
pub const NodeIdent = struct {
ident: Token,
};
pub const Parser = struct {
tokens: Iterator(Token),
allocator: std.mem.Allocator,
nodes: std.ArrayList(NodeStmt),
pub fn init(allocator: std.mem.Allocator, tokens: []Token) Parser {
return .{
.allocator = allocator,
.tokens = Iterator(Token).init(tokens),
.nodes = std.ArrayList(NodeStmt).init(allocator),
};
}
pub fn deinit(self: *Parser) void {
self.nodes.deinit();
}
fn parseExpr(self: *Parser) !NodeExpr {
return switch (self.tokens.peek().?) {
.intLit => NodeExpr{
.intLit = NodeIntlit{
.intlit = (try self.tokens.consume(.intLit)).?,
},
},
.ident => NodeExpr{
.ident = NodeIdent{
.ident = (try self.tokens.consume(.ident)).?,
},
},
else => ParsingError.InvalidExpression,
};
}
fn parseStmt(self: *Parser) !NodeStmt {
return switch (self.tokens.peek().?) {
.exit => NodeStmt{ .exit = try self.parseExit() },
.constant => NodeStmt{ .value = try self.parseValue(true) },
.variable => NodeStmt{ .value = try self.parseValue(false) },
.ident => NodeStmt{ .assign = try self.parseAssign() },
else => ParsingError.InvalidStatement,
};
}
fn parseAssign(self: *Parser) !NodeAssign {
const ident = try self.tokens.consume(.ident);
var isMutable = false;
var exists = false;
for (self.nodes.items) |item| {
switch (item) {
.value => |v| {
if (std.mem.eql(u8, v.ident.ident, ident.?.ident)) {
isMutable = !v.isConst;
exists = true;
}
},
else => {},
}
}
if (!exists) return error.UnknownIdentifier;
if (!isMutable) return error.ImmutableValue;
_ = try self.tokens.consume(.equal);
const expr = try self.parseExpr();
_ = try self.tokens.consume(.semiCol);
return NodeAssign{
.ident = ident.?,
.value = expr,
};
}
fn parseExit(self: *Parser) !NodeExit {
_ = try self.tokens.consume(.exit);
const expr = try self.parseExpr();
_ = try self.tokens.consume(.semiCol);
return NodeExit{
.expr = expr,
};
}
fn parseValue(self: *Parser, isConst: bool) !NodeValue {
self.tokens.skip();
const ident = (try self.tokens.consume(.ident)).?;
_ = try self.tokens.consume(.equal);
const expr = try self.parseExpr();
_ = try self.tokens.consume(.semiCol);
return NodeValue{
.ident = ident,
.value = expr,
.isConst = isConst,
};
}
pub fn parse(self: *Parser) ![]const NodeStmt {
while (self.tokens.peek()) |_|
try self.nodes.append(try self.parseStmt());
return self.nodes.items;
}
};
test "Parser" {
const expect = std.testing.expect;
const src = "exit 120;";
var tokenizer = tok.Tokenizer.init(std.testing.allocator, src);
defer tokenizer.deinit();
const toks = try tokenizer.tokenize();
var parser = Parser.init(std.testing.allocator, toks);
defer parser.deinit();
const parseTree = try parser.parse();
const exp: []const NodeStmt = &[_]NodeStmt{NodeStmt{
.exit = NodeExit{
.expr = NodeExpr{
.intLit = NodeIntlit{
.intlit = Token{
.intLit = 120,
},
},
},
},
}};
for (parseTree, exp) |stmt, expStmt|
try expect(std.meta.eql(stmt, expStmt));
}
|
