add number tokens

src/new_scanner.zig

@@ -11,6 +11,20 @@ pub const TokenError = error{
     Unterminated,
 };
 
+fn isDigit(char: u8) bool {
+    return char >= '0' and char <= '9';
+}
+
+fn isAlpha(c: u8) bool {
+    return (c >= 'a' and c <= 'z') or
+        (c >= 'A' and c <= 'Z') or
+        c == '_';
+}
+
+fn isAlphaNumeric(char: u8) bool {
+    return isAlpha(char) or isDigit(char);
+}
+
 pub const Scanner = struct {
     source: []const u8,
 
@@ -117,12 +131,32 @@ pub const Scanner = struct {
         return self.makeToken(.STRING);
     }
 
+    /// Consume a number
+    fn doNumber(self: *Scanner) Token {
+        while (isDigit(self.peek())) {
+            _ = self.advance();
+        }
+
+        // check if its a number like 12.34, where the '.' character
+        // exists and the one next to it is a digit.
+        if (self.peek() == '.' and isDigit(self.peekNext())) {
+            _ = self.advance();
+
+            while (isDigit(self.peek())) {
+                _ = self.advance();
+            }
+        }
+
+        return self.makeToken(.NUMBER);
+    }
+
     pub fn scanToken(self: *Scanner) !?Token {
         self.skipWhitespace();
         self.start = self.current;
         if (self.isAtEnd()) return self.makeToken(TokenType.EOF);
 
         var c = self.advance();
+        if (isDigit(c)) return self.doNumber();
 
         var token = switch (c) {
             '(' => self.makeToken(.LEFT_PAREN),