Implemented identifier detection but keywords in the programming language aren't detected yet.

scanner.c

@@ -21,6 +21,8 @@ char Peek(void);
 char PeekNext(void);
 void ParseString(TokenList *);
 void ParseNumber(TokenList *);
+void ParseIdentifier(TokenList *);
+int IsAlpha(char c);
 
 TokenList* ScanTokens(const char* source) {
     if (!source) return NULL;
@@ -181,6 +183,9 @@ void ScanToken(TokenList* tokens) {
         if (isdigit(*c)) {
             ParseNumber(tokens);
             break;
+        } else if (IsAlpha(*c)) {
+            ParseIdentifier(tokens);
+            break;
         }
 
         fprintf(stderr, "Unexcpedted character %c\n", *c);
@@ -245,4 +250,16 @@ char PeekNext() {
     if (current + 1 >= length) return '\0';
 
     return source_code[current + 1];
+}
+
+void ParseIdentifier(TokenList * list) {
+    while(IsAlpha(Peek())) Advance();
+
+    AddTokenToList(Identifier, &source_code[start], current - start, list);
+}
+
+int IsAlpha(char c) {
+    return  (c >= 'a' && c <= 'z') ||
+            (c >= 'A' && c <= 'Z') ||
+            (c == '_');
 }