Add C Integer semantics experiment

contrib/c-integer-semantics.py

+#!/usr/bin/env python
+# coding: utf-8
+
+from os import system
+import ctypes
+
+C_SRC = """
+#include <stdlib.h>
+#include <stdint.h>
+
+int64_t cdiv(int64_t a, int64_t b)
+{
+    return a/b;
+}
+
+int64_t cmod(int64_t a, int64_t b)
+{
+    return a%b;
+}
+
+#define LOOPY_CALL_WITH_INTEGER_TYPES(MACRO_NAME) \
+    MACRO_NAME(short) \
+    MACRO_NAME(int) \
+    MACRO_NAME(long) \
+    MACRO_NAME(int64_t)
+
+#define LOOPY_DEFINE_FLOOR_DIV(TYPE) \
+    TYPE loopy_floor_div_##TYPE(TYPE a, TYPE b) \
+    { \
+        if ((a<0) != (b<0)) \
+            a = a - (b + (b<0) - (b>=0)); \
+        return a/b; \
+    }
+
+LOOPY_CALL_WITH_INTEGER_TYPES(LOOPY_DEFINE_FLOOR_DIV)
+#undef LOOPY_DEFINE_FLOOR_DIV
+
+#define LOOPY_DEFINE_FLOOR_DIV_POS_B(TYPE) \
+    TYPE loopy_floor_div_pos_b_##TYPE(TYPE a, TYPE b) \
+    { \
+        if (a<0) \
+            a = a - (b-1); \
+        return a/b; \
+    }
+
+LOOPY_CALL_WITH_INTEGER_TYPES(LOOPY_DEFINE_FLOOR_DIV_POS_B)
+#undef LOOPY_DEFINE_FLOOR_DIV_POS_B
+
+
+#define LOOPY_DEFINE_MOD_POS_B(TYPE) \
+    TYPE loopy_mod_pos_b_##TYPE(TYPE a, TYPE b) \
+    { \
+        TYPE result = a%b; \
+        if (result < 0) \
+            result += b; \
+        return result; \
+    }
+
+LOOPY_CALL_WITH_INTEGER_TYPES(LOOPY_DEFINE_MOD_POS_B)
+#undef LOOPY_DEFINE_MOD_POS_B
+
+#define LOOPY_DEFINE_MOD(TYPE) \
+    TYPE loopy_mod_##TYPE(TYPE a, TYPE b) \
+    { \
+        TYPE result = a%b; \
+        if (result < 0 && b > 0) \
+            result += b; \
+        if (result > 0 && b < 0) \
+            result = result + b; \
+        return result; \
+    }
+
+LOOPY_CALL_WITH_INTEGER_TYPES(LOOPY_DEFINE_MOD)
+#undef LOOPY_DEFINE_MOD
+
+
+"""
+
+
+def main():
+    with open("int-experiments.c", "w") as outf:
+        outf.write(C_SRC)
+
+    system('gcc -Wall -shared int-experiments.c -o int-experiments.so')
+
+    int_exp = ctypes.CDLL("int-experiments.so")
+    for func in [
+            int_exp.cdiv,
+            int_exp.cmod,
+            int_exp.loopy_floor_div_int64_t,
+            int_exp.loopy_floor_div_pos_b_int64_t,
+            int_exp.loopy_mod_pos_b_int64_t,
+            int_exp.loopy_mod_int64_t,
+            ]:
+        func.argtypes = [ctypes.c_longlong, ctypes.c_longlong]
+        func.restype = ctypes.c_longlong
+
+    cdiv = int_exp.cdiv  # noqa
+    cmod = int_exp.cmod  # noqa
+    int_floor_div = int_exp.loopy_floor_div_int64_t
+    int_floor_div_pos_b = int_exp.loopy_floor_div_pos_b_int64_t
+    int_mod_pos_b = int_exp.loopy_mod_pos_b_int64_t
+    int_mod = int_exp.loopy_mod_int64_t
+
+    m = 50
+
+    for a in range(-m, m):
+        for b in range(1, m):
+            cresult = int_floor_div_pos_b(a, b)
+            presult = a // b
+            assert cresult == presult
+            if cresult != presult:
+                print(a, b, cresult, presult)
+
+    for a in range(-m, m):
+        for b in range(-m, m):
+            if b == 0:
+                continue
+
+            cresult = int_floor_div(a, b)
+            presult = a // b
+            assert cresult == presult
+            if cresult != presult:
+                print(a, b, cresult, presult)
+
+    for a in range(-m, m):
+        for b in range(1, m):
+            cresult = int_mod_pos_b(a, b)
+            presult = a % b
+            assert cresult == presult
+
+    for a in range(-m, m):
+        for b in range(-m, m):
+            if b == 0:
+                continue
+
+            cresult = int_mod(a, b)
+            presult = a % b
+            assert cresult == presult
+            if cresult != presult:
+                print(a, b, cresult, presult)
+
+
+if __name__ == "__main__":
+    main()