Update leibniz.cpp

src/leibniz.cpp

@@ -1,31 +1,31 @@
-#include <cstdio>
-#include <cstdlib>
-
-unsigned rounds;
-double pi = 1.0;
+#include <iostream>
+#include <fstream>
 
 int main()
 {
-    auto infile = std::fopen("rounds.txt", "r");    // open file
-    if (infile == NULL) {
-        perror("open file");
-        return EXIT_FAILURE;
-    }
-    if (std::fscanf(infile, "%u", &rounds) != 1) {  // read from file
+    long rounds{0};
+
+    std::ifstream infile("rounds.txt");   // open file
+    if (!(infile >> rounds))
+    {
         perror("read file");
         return EXIT_FAILURE;
     }
-    std::fclose(infile);                            // close file
+    infile.close();                            // close file
+
+    double x {1.0};
+    double pi {1.0};
 
-    rounds += 2u; // do this outside the loop
+    rounds += 2; // do this outside the loop
 
-    for (unsigned i=2u ; i < rounds ; ++i) // use ++i instead of i++
+    for (long i {2} ; i < rounds ; i++) // use ++i instead of i++
     {
-        double x = -1.0 + 2.0 * (i & 0x1); // allows vectorization
-        pi += (x / (2u * i - 1u)); // double / unsigned = double
+        x = -1.0 + 2.0 * (i & 0x1); // allows vectorization
+        pi += (x / (2 * i - 1)); // double / unsigned = double
     }
 
     pi *= 4;
-    std::printf("%.16f\n", pi); // print 16 decimal digits of pi
+    std::cout.precision(16);
+    std::cout << pi; // print 16 decimal digits of pi
     return EXIT_SUCCESS;
 }