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const std = @import("std");
pub const Token = struct {
loc: Location,
type: Type,
pub const Type = enum {
left_paren,
right_paren,
left_curly,
right_curly,
integer_literal,
plus,
minus,
equal,
invalid,
eof,
identifier,
// Keywords
let,
@"if",
@"else",
};
};
pub const Location = struct {
start: usize,
end: usize,
pub fn combine(a: Location, b: Location) Location {
std.debug.assert(a.end <= b.start);
return .{ .start = @min(a.start, b.start), .end = @max(a.end, b.end) };
}
/// Assumes that the location comes directly from an `integer_literal` token.
pub fn getInt(self: Location, file_source: []const u8) u64 {
var value: u64 = 0;
for (file_source[self.start..self.end]) |c| {
std.debug.assert('0' <= c and c <= '9');
value = value * 10 + (c - '0');
}
return value;
}
/// Assumes that the location comes directly from an `identifier` token.
pub fn getIdent(self: Location, file_source: []const u8) []const u8 {
return file_source[self.start..self.end];
}
};
pub fn peek(self: *Self) Token {
if (self.peeked == null) {
self.peeked = self.getNext();
}
return self.peeked.?;
}
pub fn next(self: *Self) Token {
const token = self.peek();
self.peeked = null;
return token;
}
source: []const u8,
start: usize = 0,
pos: usize = 0,
peeked: ?Token = null,
fn getNext(self: *Self) Token {
self.start = self.pos;
return s: switch (self.eatChar() orelse return self.create(.eof)) {
'(' => self.create(.left_paren),
')' => self.create(.right_paren),
'{' => self.create(.left_curly),
'}' => self.create(.right_curly),
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9' => self.integerLiteral(),
'+' => self.create(.plus),
'-' => self.create(.minus),
'=' => self.create(.equal),
'#' => {
while ((self.eatChar() orelse '\n') != '\n') {}
self.start = self.pos;
continue :s (self.eatChar() orelse return self.create(.eof));
},
' ', '\n' => {
self.start = self.pos;
continue :s (self.eatChar() orelse return self.create(.eof));
},
else => |c| if ('a' <= c and c <= 'z' or 'A' <= c and c <= 'Z')
self.identifierOrKeyword()
else
self.create(.invalid),
};
}
fn integerLiteral(self: *Self) Token {
var value: ?u64 = self.source[self.start] - '0';
while (digitValue(self.peekChar())) |v| {
var nxt: ?u64 = null;
if (value) |val|
if (std.math.mul(u64, val, 10) catch null) |p|
if (std.math.add(u64, p, v) catch null) |s| {
nxt = s;
};
value = nxt;
_ = self.eatChar();
}
return if (value != null)
self.create(.integer_literal)
else
self.create(.invalid);
}
fn identifierOrKeyword(self: *Self) Token {
while (true) {
const c = self.peekChar() orelse 0;
if ('a' <= c and c <= 'z' or 'A' <= c and c <= 'Z' or c == '_') {
_ = self.eatChar();
continue;
}
const value = self.source[self.start..self.pos];
return self.create(switch (std.meta.stringToEnum(Token.Type, value) orelse .invalid) {
.let, .@"if", .@"else" => |t| t,
else => .identifier,
});
}
}
fn create(self: *Self, ty: Token.Type) Token {
const start = self.start;
return .{ .loc = .{ .start = start, .end = self.pos }, .type = ty };
}
fn eatChar(self: *Self) ?u8 {
const token = self.peekChar();
if (token != null) self.pos += 1;
return token;
}
fn peekChar(self: *Self) ?u8 {
return if (self.pos < self.source.len) self.source[self.pos] else null;
}
const Self = @This();
fn digitValue(c: ?u8) ?u8 {
return switch (c orelse return null) {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9' => c.? - '0',
else => null,
};
}
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