Lexer using struct

Exercise 4/Lexer.h

@@ -0,0 +1,31 @@
+/* symbols */
+#define _LETTER_ 1
+#define _DIGIT_ 2
+#define _OPERATOR_ 3
+#define _PUNCTUATION_ 4
+#define _END_OF_LINE_ 5
+#define _UNKNOWN_ 10
+
+/* state */
+#define _START_ 100
+#define _GET_NEXT_CHARACTER_ 110
+#define _READ_IDENTIFIER_ 120
+#define _READ_NUM_LIT_ 130
+#define _READ_OPERATOR_ 140
+#define _READ_PUNCTUATION_ 150
+#define _STOP_ 999
+#define _ERROR_ 1000
+
+// lexer struct
+struct Lexer_s {
+        int state;
+        char* source_code;
+        char** current_pos;
+    };
+
+// typedef
+typedef struct Lexer_s Lexer_t;
+
+// methods
+void init_Lexer(Lexer_t*, char*);
+void run_Lexer(Lexer_t*);