Create jinc.cpp

UTSR/jinc.cpp

@@ -0,0 +1,22 @@
+#include <cmath>
+#include <vector>
+#include <algorithm>
+
+double jinc(double r) {
+    // Returns the jinc function [J1(2*pi*r)/(2*pi*r)] evaluated at r.
+    // Per this definition, the first zero of jinc function is at 0.61.
+    if (r == 0.0) {
+        return 0.5;
+    }
+    return std::real(std::cyl_bessel_j(1, r) / r);
+}
+
+std::vector<double> jinc(const std::vector<double>& r) {
+    std::vector<double> y(r.size());
+    std::transform(r.begin(), r.end(), y.begin(), [](double x) {
+        return jinc(x);
+    });
+    return y;
+}
+
+