diff --git a/tiny/lisp-nontail.c b/tiny/lisp-nontail.c
index b8ff3a4..9f6a916 100644
--- a/tiny/lisp-nontail.c
+++ b/tiny/lisp-nontail.c
@@ -27,15 +27,10 @@
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef __LP64__
-#define NUM_FORMAT "%" PRId64
-typedef uint64_t value_t;
-typedef int64_t number_t;
-#else
-#define NUM_FORMAT "%" PRId32
-typedef uint32_t value_t;
-typedef int32_t number_t;
-#endif
+#define NUM_FORMAT "%" PRIdPTR
+
+typedef intptr_t number_t;
+typedef uintptr_t value_t;
 
 typedef struct {
     value_t car;
diff --git a/tiny/lisp.c b/tiny/lisp.c
index 1e99ebc..061362f 100644
--- a/tiny/lisp.c
+++ b/tiny/lisp.c
@@ -27,15 +27,10 @@
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef __LP64__
-#define NUM_FORMAT "%" PRId64
-typedef uint64_t value_t;
-typedef int64_t number_t;
-#else
-#define NUM_FORMAT "%" PRId32
-typedef uint32_t value_t;
-typedef int32_t number_t;
-#endif
+#define NUM_FORMAT "%" PRIdPTR
+
+typedef intptr_t number_t;
+typedef uintptr_t value_t;
 
 typedef struct {
     value_t car;
diff --git a/tiny/lisp2.c b/tiny/lisp2.c
index 69a1b5f..782a819 100644
--- a/tiny/lisp2.c
+++ b/tiny/lisp2.c
@@ -48,15 +48,10 @@
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef __LP64__
-#define NUM_FORMAT "%" PRId64
-typedef uint64_t value_t;
-typedef int64_t number_t;
-#else
-#define NUM_FORMAT "%" PRId32
-typedef uint32_t value_t;
-typedef int32_t number_t;
-#endif
+#define NUM_FORMAT "%" PRIdPTR
+
+typedef intptr_t number_t;
+typedef uintptr_t value_t;
 
 typedef struct {
     value_t car;
diff --git a/tiny/lispf.c b/tiny/lispf.c
index 9b88b1f..e401335 100644
--- a/tiny/lispf.c
+++ b/tiny/lispf.c
@@ -33,25 +33,16 @@
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef __LP64__
-typedef uint64_t value_t;
-#else
-typedef uint32_t value_t;
-#endif
-
 #ifdef FLOAT
 #define NUM_FORMAT "%f"
 typedef float number_t;
 #else
-#ifdef __LP64__
-#define NUM_FORMAT "%" PRId64
-typedef int64_t number_t;
-#else
-#define NUM_FORMAT "%" PRId32
-typedef int32_t number_t;
-#endif
+#define NUM_FORMAT "%" PRIdPTR
+typedef intptr_t number_t;
 #endif
 
+typedef uintptr_t value_t;
+
 typedef struct {
     value_t car;
     value_t cdr;