add consumption of comments and strings

src/main.zig

@@ -14,7 +14,15 @@ fn run(allocator: *Allocator, data: []u8) !void {
     var it = tokens.iterator();
 
     while (it.next()) |token| {
-        try token.Simple.printToken(stdout);
+        switch (token) {
+            .Simple => |value| {
+                try value.printToken(stdout);
+            },
+            .Slice => |value| {
+                try value.printToken(stdout);
+            },
+        }
+
         hadError = false;
     }
 }

src/scanner.zig

@@ -44,6 +44,17 @@ pub const Scanner = struct {
         });
     }
 
+    fn addSliceToken(self: *Scanner, ttype: token.TokenType, slice: []u8) !void {
+        try self.addToken(token.Token{
+            .Slice = token.SliceToken.init(
+                ttype,
+                self.currentLexeme(),
+                self.line,
+                slice,
+            ),
+        });
+    }
+
     fn addToken(
         self: *Scanner,
         tok: token.Token,
@@ -51,6 +62,59 @@ pub const Scanner = struct {
         try self.tokens.append(tok);
     }
 
+    /// Check if the next character matches what is expected.
+    fn match(self: *Scanner, expected: u8) bool {
+        if (self.isAtEnd()) return false;
+        if (self.source[self.current] != expected) return false;
+
+        self.current += 1;
+        return true;
+    }
+
+    /// Add a SimpleToken of type_match if the next character is
+    /// `expected`. Adds a SimpleToken of type_nomatch when it is not.
+    fn addMatchToken(
+        self: *Scanner,
+        expected: u8,
+        type_match: token.TokenType,
+        type_nomatch: token.TokenType,
+    ) !void {
+        if (self.match(expected)) {
+            try self.addSimpleToken(type_match);
+        } else {
+            try self.addSimpleToken(type_nomatch);
+        }
+    }
+
+    fn peek(self: *Scanner) u8 {
+        if (self.isAtEnd()) return 0;
+        return self.source[self.current];
+    }
+
+    fn doString(self: *Scanner) !void {
+        // consume entire string
+        while (self.peek() != '"' and !self.isAtEnd()) {
+            if (self.peek() == '\n') self.line += 1;
+            _ = self.advance();
+        }
+
+        // unterminated string.
+        if (self.isAtEnd()) {
+            try main.doError(self.line, "Unterminated string.");
+            return;
+        }
+
+        // the closing ".
+        _ = self.advance();
+
+        // trim the surrounding quotes.
+        try self.addSliceToken(
+            .STRING,
+            self.source[self.start + 1 .. self.current - 1],
+        );
+    }
+
+    /// Scan through our tokens and add them to the Scanner's token list.
     fn scanToken(self: *Scanner) !void {
         var c = self.advance();
 
@@ -65,6 +129,30 @@ pub const Scanner = struct {
             '+' => try self.addSimpleToken(.PLUS),
             ';' => try self.addSimpleToken(.SEMICOLON),
             '*' => try self.addSimpleToken(.STAR),
+
+            '!' => try self.addMatchToken('=', .BANG_EQUAL, .BANG),
+            '=' => try self.addMatchToken('=', .EQUAL_EQUAL, .EQUAL),
+            '<' => try self.addMatchToken('=', .LESS_EQUAL, .LESS),
+            '>' => try self.addMatchToken('=', .GREATER_EQUAL, .GREATER),
+
+            '/' => blk: {
+                // consume comments
+                if (self.match('/')) {
+                    while (self.peek() != '\n' and !self.isAtEnd()) {
+                        _ = self.advance();
+                    }
+                } else {
+                    try self.addSimpleToken(.SLASH);
+                }
+            },
+
+            ' ', '\r', '\t' => blk: {},
+            '\n' => blk: {
+                self.line += 1;
+            },
+
+            '"' => try self.doString(),
+
             else => {
                 try main.doError(self.line, "Unexpected character");
             },

src/token.zig

@@ -76,18 +76,30 @@ pub fn TokenFactory(
         }
 
         pub fn printToken(self: Self, stdout: var) !void {
+            if (T == void) {
                 try stdout.print(
-                "Token(type={x}, lexeme='{}', line={}\n",
+                    "Token(type={x}, lexeme='{}', line={})\n",
                     self.ttype,
                     self.lexeme,
                     self.line,
                 );
+            } else {
+                try stdout.print(
+                    "Token(type={x}, lexeme='{}', line={} literal='{}')\n",
+                    self.ttype,
+                    self.lexeme,
+                    self.line,
+                    self.literal,
+                );
+            }
         }
     };
 }
 
 pub const SimpleToken = TokenFactory(void);
+pub const SliceToken = TokenFactory([]u8);
 
-pub const Token = union {
+pub const Token = union(enum) {
     Simple: SimpleToken,
+    Slice: SliceToken,
 };