diff --git a/SLS_C/include/sls/lexer.h b/SLS_C/include/sls/lexer.h
index 18d34af..5d72eab 100644
--- a/SLS_C/include/sls/lexer.h
+++ b/SLS_C/include/sls/lexer.h
@@ -49,7 +49,19 @@ typedef struct {
 } StringLiteral;
 
 typedef struct {
-    // TODO
+    TokenType type;
+    union {
+        Identifier *identifiers;
+        IntegerLiteral *integer_literals;
+        float *float_literals;
+        double *double_literals;
+        StringLiteral *string_literals;
+        uint8_t *boolean_literals;
+        ArrayLiteral *array_literals;
+        TokenString *token_strings;
+        TypeTuple *type_tuples;
+    };
+    size_t length;
 } ArrayLiteral;
 
 typedef struct {
@@ -58,7 +70,10 @@ typedef struct {
 } TokenString;
 
 typedef struct {
-    // TODO
+    Identifier *input_identifiers;
+    size_t input_length;
+    Identifier *output_identifiers;
+    size_t output_length;
 } TypeTuple;
 
 typedef struct {