diff --git a/include/custom.h b/include/custom.h
index 46eb0b5..f58e0db 100644
--- a/include/custom.h
+++ b/include/custom.h
@@ -1,12 +1,28 @@
 #ifndef LIBABACUS_CUSTOM_H
 #define LIBABACUS_CUSTOM_H
 
+#include "parsetype.h"
+
 /**
  * A function pointer that is called
  * to execute a certain type of function.
  */
 typedef void(*libab_function_ptr)();
 
+/**
+ * The common information
+ * that both operators and functions shared.
+ */
+struct libab_behavior_s {
+    /**
+     * The function that handles the parameters.
+     */
+    libab_function_ptr function;
+    /**
+     * The type of the function.
+     */
+    libab_parsetype* type;
+};
 /**
  * A struct that holds informatiion
  * about an operator that has been
@@ -22,9 +38,9 @@ struct libab_operator_s {
      */
     int associativity;
     /**
-     * The functionality of the operator.
+     * The behavior of this operator.
      */
-    libab_function_ptr function;
+    struct libab_behavior_s behavior;
 };
 
 /**
@@ -34,11 +50,12 @@ struct libab_operator_s {
  */
 struct libab_function_s {
     /**
-     * The functionality of the function.
+     * The behavior of this function.
      */
-    libab_function_ptr function;
+    struct libab_behavior_s behavior;
 };
 
+typedef struct libab_behavior_s libab_behavior;
 typedef struct libab_operator_s libab_operator;
 typedef struct libab_function_s libab_function;
 
diff --git a/include/libabacus.h b/include/libabacus.h
index 728d523..da9124d 100644
--- a/include/libabacus.h
+++ b/include/libabacus.h
@@ -46,37 +46,41 @@ libab_result libab_init(libab* ab);
  * @param op the operator string to register.
  * @param precedence the precedence of the operator.
  * @param associativity the associativity of the operator.
+ * @param type the type of this operator.
  * @param func the function that describes the functionality of the operator.
  * @return the result of the initialization.
  */
-libab_result libab_register_operator_infix(libab* ab, const char* op, int precedence, int associativity, libab_function_ptr func);
+libab_result libab_register_operator_infix(libab* ab, const char* op, int precedence, int associativity, const char* type, libab_function_ptr func);
 /**
  * Registers an operation with libabacus that appears
  * before its operand.
  * @param ab the libabacus instance to register the operator with.
  * @param op the operator string to register.
+ * @param type the type of this operator.
  * @param func the function that describes the functionality of the operator.
  * @return the result of the registration.
  */
-libab_result libab_register_operator_prefix(libab* ab, const char* op, libab_function_ptr func);
+libab_result libab_register_operator_prefix(libab* ab, const char* op, const char* type, libab_function_ptr func);
 /**
  * Registers an operation with libabacus that appears
  * after its operand.
  * @param ab the libabacus instance to register the operator with.
  * @param op the operator string to register.
+ * @param type the type of this operator.
  * @param func the function that describes the functionality of the operator.
  * @return the result of the registration.
  */
-libab_result libab_register_operator_postfix(libab* ab, const char* op, libab_function_ptr func);
+libab_result libab_register_operator_postfix(libab* ab, const char* op, const char* type, libab_function_ptr func);
 
 /**
  * Registers a function with libabacus.
  * @param ab the libabacus instance used to keep state.
  * @param name the name of the function.
+ * @param type the type of this operator.
  * @param func the function that describes the functionality of the function.
  * @return the result of the initialization.
  */
-libab_result libab_register_function(libab* ab, const char* name, libab_function_ptr func);
+libab_result libab_register_function(libab* ab, const char* name, const char* type, libab_function_ptr func);
 /**
  * Releases all the resources allocated by libabacus.
  * @param ab the libabacus instance to release.
diff --git a/src/libabacus.c b/src/libabacus.c
index 3c64e91..837adbb 100644
--- a/src/libabacus.c
+++ b/src/libabacus.c
@@ -17,19 +17,41 @@ void _sanitize(char* to, const char* from, size_t buffer_size) {
     to[index] = '\0';
 }
 
-libab_result _register_operator(libab* ab, const char* op, int token_type, int precedence, int associativity, libab_function_ptr func) {
+libab_result _initialize_behavior(libab* ab, libab_behavior* behavior, 
+        const char* type, libab_function_ptr func) {
+    libab_result result = LIBAB_SUCCESS;
+    ll tokens;
+
+    ll_init(&tokens);
+
+    result = libab_lexer_lex(&ab->lexer, type, &tokens);
+    if(result == LIBAB_SUCCESS) {
+        result = libab_parser_parse_type(&ab->parser, &tokens, type, &behavior->type);
+    }
+
+    ll_foreach(&tokens, NULL, compare_always, libab_lexer_foreach_match_free);
+    ll_free(&tokens);
+
+    return result;
+}
+
+libab_result _register_operator(libab* ab, const char* op, int token_type, int precedence, int associativity, const char* type, libab_function_ptr func) {
     char op_buffer[8];
     libab_result result = LIBAB_SUCCESS;
     libab_table_entry* new_entry;
     if((new_entry = malloc(sizeof(*new_entry)))) {
         new_entry->variant = ENTRY_OP;
-        new_entry->data_u.op.function = func;
+        new_entry->data_u.op.behavior.type = NULL;
         new_entry->data_u.op.precedence = precedence;
         new_entry->data_u.op.associativity = associativity;
     } else {
         result = LIBAB_MALLOC;
     }
 
+    if(result == LIBAB_SUCCESS) {
+        result = _initialize_behavior(ab, &(new_entry->data_u.op.behavior), type, func);
+    }
+
     if(result == LIBAB_SUCCESS) {
         _sanitize(op_buffer, op, 8);
         result = libab_convert_lex_result(eval_config_add(&ab->lexer.config, op_buffer, token_type));
@@ -40,6 +62,8 @@ libab_result _register_operator(libab* ab, const char* op, int token_type, int p
     }
 
     if(result != LIBAB_SUCCESS) {
+        if(new_entry && new_entry->data_u.op.behavior.type)
+            libab_parsetype_free_recursive(new_entry->data_u.op.behavior.type);
         eval_config_remove(&ab->lexer.config, op, token_type);
         free(new_entry);
     }
@@ -47,33 +71,40 @@ libab_result _register_operator(libab* ab, const char* op, int token_type, int p
     return result;
 }
 
-libab_result libab_register_operator_infix(libab* ab, const char* op, int precedence, int associativity, libab_function_ptr func) {
-    return _register_operator(ab, op, TOKEN_OP_INFIX, precedence, associativity, func);
+libab_result libab_register_operator_infix(libab* ab, const char* op, int precedence, int associativity, const char* type, libab_function_ptr func) {
+    return _register_operator(ab, op, TOKEN_OP_INFIX, precedence, associativity, type, func);
 }
 
-libab_result libab_register_operator_prefix(libab* ab, const char* op, libab_function_ptr func) {
-    return _register_operator(ab, op, TOKEN_OP_PREFIX, 0, 0, func);
+libab_result libab_register_operator_prefix(libab* ab, const char* op, const char* type, libab_function_ptr func) {
+    return _register_operator(ab, op, TOKEN_OP_PREFIX, 0, 0, type, func);
 }
 
-libab_result libab_register_operator_postfix(libab* ab, const char* op, libab_function_ptr func) {
-    return _register_operator(ab, op, TOKEN_OP_POSTFIX, 0, 0, func);
+libab_result libab_register_operator_postfix(libab* ab, const char* op, const char* type, libab_function_ptr func) {
+    return _register_operator(ab, op, TOKEN_OP_POSTFIX, 0, 0, type, func);
 }
 
-libab_result libab_register_function(libab* ab, const char* name, libab_function_ptr func) {
+libab_result libab_register_function(libab* ab, const char* name, const char* type, libab_function_ptr func) {
     libab_result result = LIBAB_SUCCESS;
     libab_table_entry* new_entry;
     if((new_entry = malloc(sizeof(*new_entry)))) {
         new_entry->variant = ENTRY_FUN;
-        new_entry->data_u.function.function = func;
+        new_entry->data_u.function.behavior.type = NULL;
     } else {
         result = LIBAB_MALLOC;
     }
 
+    if(result == LIBAB_SUCCESS) {
+        result = _initialize_behavior(ab, 
+                &(new_entry->data_u.function.behavior), type, func);
+    }
+
     if(result == LIBAB_SUCCESS) {
         result = libab_table_put(&ab->table, name, new_entry);
     }
 
     if(result != LIBAB_SUCCESS) {
+        if(new_entry && new_entry->data_u.function.behavior.type)
+            libab_parsetype_free_recursive(new_entry->data_u.function.behavior.type);
         free(new_entry);
     }
 
diff --git a/src/table.c b/src/table.c
index c70d2f9..ef54631 100644
--- a/src/table.c
+++ b/src/table.c
@@ -43,5 +43,9 @@ void libab_table_free(libab_table* table) {
     ht_free(&table->table);
 }
 void libab_table_entry_free(libab_table_entry* entry) {
-    
+    if(entry->variant == ENTRY_OP) {
+        libab_parsetype_free_recursive(entry->data_u.op.behavior.type);
+    } else if(entry->variant == ENTRY_FUN) {
+        libab_parsetype_free_recursive(entry->data_u.function.behavior.type);
+    }
 }