diff --git a/include/ap_common.h b/include/ap_common.h
index b49b7e2..75b0d8f 100644
--- a/include/ap_common.h
+++ b/include/ap_common.h
@@ -56,9 +56,9 @@
 #include <ap_decl.h>
 
 // TODO Undefine in open-source release.
-#define _AP_ENABLE_HALF_ 1
+// #define _AP_ENABLE_HALF_ 1
 
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
 // Before ap_private definition.
 #ifdef __SYNTHESIS__
 #define _HLS_HALF_DEFINED_
@@ -168,8 +168,7 @@ class half;
 #endif
 
 // for detecting if char is signed.
-#include <climits>
-enum { CHAR_IS_SIGNED = CHAR_MIN < 0 };
+enum { CHAR_IS_SIGNED = (char)-1 < 0 };
 
 // TODO we have similar traits in x_hls_utils.h, should consider unify.
 namespace _ap_type {
@@ -702,7 +701,7 @@ INLINE unsigned int floatToRawBits(float pf) {
   return LD.__L;
 }
 
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
 INLINE unsigned short halfToRawBits(half pf) {
 #ifdef __SYNTHESIS__
   union {
@@ -737,7 +736,7 @@ INLINE float rawBitsToFloat(unsigned long pi) {
   return LD.__D;
 }
 
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
 // short is at least 16-bit
 INLINE half rawBitsToHalf(unsigned short pi) {
 #ifdef __SYNTHESIS__
diff --git a/include/ap_fixed.h b/include/ap_fixed.h
index 631e1b4..1847c49 100644
--- a/include/ap_fixed.h
+++ b/include/ap_fixed.h
@@ -174,7 +174,7 @@ struct ap_fixed : ap_fixed_base<_AP_W, _AP_I, true, _AP_Q, _AP_O, _AP_N> {
   CTOR(unsigned long)
   CTOR(ap_slong)
   CTOR(ap_ulong)
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
   CTOR(half)
 #endif
   CTOR(float)
@@ -324,7 +324,7 @@ struct ap_ufixed : ap_fixed_base<_AP_W, _AP_I, false, _AP_Q, _AP_O, _AP_N> {
   CTOR(unsigned long)
   CTOR(ap_slong)
   CTOR(ap_ulong)
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
   CTOR(half)
 #endif
   CTOR(float)
diff --git a/include/ap_fixed_base.h b/include/ap_fixed_base.h
index f486574..411679d 100644
--- a/include/ap_fixed_base.h
+++ b/include/ap_fixed_base.h
@@ -59,7 +59,7 @@
 // for ap_int_base and its reference types.
 #include <ap_int.h>
 #ifndef __SYNTHESIS__
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
 // for half type
 #include <hls_half.h>
 #endif
@@ -671,7 +671,7 @@ struct ap_fixed_base : _AP_ROOT_TYPE<_AP_W, _AP_S> {
   // TODO more optimized implementation.
   INLINE ap_fixed_base(float d) { *this = ap_fixed_base(double(d)); }
 
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
   // TODO more optimized implementation.
   INLINE ap_fixed_base(half d) { *this = ap_fixed_base(double(d)); }
 #endif
@@ -973,7 +973,7 @@ struct ap_fixed_base : _AP_ROOT_TYPE<_AP_W, _AP_S> {
     return rawBitsToFloat(m);
   }
 
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
   /// convert function to half.
   /** only round-half-to-even mode supported, does not obey FE env. */
   INLINE half to_half() const {
@@ -1029,7 +1029,7 @@ struct ap_fixed_base : _AP_ROOT_TYPE<_AP_W, _AP_S> {
 
   INLINE operator float() const { return to_float(); }
 
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
   INLINE operator half() const { return to_half(); }
 #endif
 
diff --git a/include/ap_int.h b/include/ap_int.h
index a0831c0..af2e805 100644
--- a/include/ap_int.h
+++ b/include/ap_int.h
@@ -156,7 +156,7 @@ struct ap_int : ap_int_base<_AP_W, true> {
 #undef CTOR
   ap_int(double val) : Base(val) {}
   ap_int(float val) : Base(val) {}
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
   ap_int(half val) : Base(val) {}
 #endif
 
@@ -290,7 +290,7 @@ struct ap_uint : ap_int_base<_AP_W, false> {
 #undef CTOR
   ap_uint(double val) : Base(val) {}
   ap_uint(float val) : Base(val) {}
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
   ap_uint(half val) : Base(val) {}
 #endif
 
diff --git a/include/ap_int_base.h b/include/ap_int_base.h
index 720c9d7..aea2009 100644
--- a/include/ap_int_base.h
+++ b/include/ap_int_base.h
@@ -62,16 +62,13 @@
 
 #include <ap_common.h>
 #ifndef __SYNTHESIS__
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
 #include <hls_half.h>
 #endif
 #include <iostream>
 #include <string.h>
 #endif
 
-// for ptrdiff_t used in increasing pointer.
-#include <cstddef>
-
 /* ----------------------------------------------------------------
  * ap_int_base: AutoPilot integer/Arbitrary precision integer.
  * ----------------------------------------------------------------
@@ -251,7 +248,7 @@ struct ap_int_base : public _AP_ROOT_TYPE<_AP_W, _AP_S> {
   CTOR_FROM_INT(ap_ulong, _AP_SIZE_ap_slong, false)
 #undef CTOR_FROM_INT
 
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
   /// ctor from half.
   //  TODO optimize
   INLINE ap_int_base(half op) {
@@ -1391,13 +1388,13 @@ OP_BIN_AP2(%, mod)
   template <typename PTR_TYPE, int _AP_W, bool _AP_S>                     \
   INLINE PTR_TYPE* operator BIN_OP(PTR_TYPE* i_op,                        \
                                    const ap_int_base<_AP_W, _AP_S>& op) { \
-    std::ptrdiff_t op2 = op.to_long(); /* Not all implementation */            \
+    ap_slong op2 = op.to_int64(); /* Not all implementation */            \
     return i_op BIN_OP op2;                                               \
   }                                                                       \
   template <typename PTR_TYPE, int _AP_W, bool _AP_S>                     \
   INLINE PTR_TYPE* operator BIN_OP(const ap_int_base<_AP_W, _AP_S>& op,   \
                                    PTR_TYPE* i_op) {                      \
-    std::ptrdiff_t op2 = op.to_long(); /* Not all implementation */            \
+    ap_slong op2 = op.to_int64(); /* Not all implementation */            \
     return op2 BIN_OP i_op;                                               \
   }
 
@@ -1429,7 +1426,7 @@ OP_BIN_WITH_PTR(-)
   OP_BIN_WITH_FLOAT(+, C_TYPE) \
   OP_BIN_WITH_FLOAT(-, C_TYPE)
 
-#ifdef _AP_ENABLE_HALF_
+#if _AP_ENABLE_HALF_ == 1
 ALL_OP_WITH_FLOAT(half)
 #endif
 ALL_OP_WITH_FLOAT(float)