去除了 tsub_ok.c 中的 if 语句

chapter2/code/tsub-ok.c

@@ -6,17 +6,19 @@
 #include <limits.h>
 
 /* Determine whether arguments can be substracted without overflow */
-int tsub_ok(int x, int y) {
-  if (y == INT_MIN) {
-    return 0;
-  }
+int tsub_ok(int x, int y)
+{
+    int res = 1;
 
-  int neg_y = -y;
-  int sum = x + neg_y;
-  int pos_over = x > 0 && neg_y > 0 && sum < 0;
-  int neg_over = x < 0 && neg_y < 0 && sum >= 0;
+    (y == INT_MIN) && (res = 0);
 
-  return !(pos_over || neg_over);
+    int sub = x - y;
+    int pos_over = x > 0 && y < 0 && sub < 0;
+    int neg_over = x < 0 && y > 0 && sub > 0;
+
+    res = res && !(pos_over || neg_over);
+
+    return res;
 }
 
 int main(int argc, char* argv[]) {