[rand.dist.samp.pconst] plus some bug fixes in the tests of the other distributions

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@104224 91177308-0d34-0410-b5e6-96231b3b80d8

test/numerics/rand/rand.dis/rand.dist.samp/rand.dist.samp.pconst/ctor_param.pass.cpp

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <random>
+
+// template<class RealType = double>
+// class piecewise_constant_distribution
+
+// explicit piecewise_constant_distribution(const param_type& parm);
+
+#include <random>
+#include <cassert>
+
+int main()
+{
+    {
+        typedef std::piecewise_constant_distribution<> D;
+        typedef D::param_type P;
+        double b[] = {10, 14, 16, 17};
+        double p[] = {25, 62.5, 12.5};
+        P pa(b, b+4, p);
+        D d(pa);
+        std::vector<double> iv = d.intervals();
+        assert(iv.size() == 4);
+        assert(iv[0] == 10);
+        assert(iv[1] == 14);
+        assert(iv[2] == 16);
+        assert(iv[3] == 17);
+        std::vector<double> dn = d.densities();
+        assert(dn.size() == 3);
+        assert(dn[0] == .0625);
+        assert(dn[1] == .3125);
+        assert(dn[2] == .125);
+    }
+}