Merge pull request #643 from stan-dev/issue-123

Issue 123
stan-dev · Feb 8, 2018 · 5ea9efa · 5ea9efa
2 parents a4c9203 + 8200065
commit 5ea9efa
Show file tree

Hide file tree

Showing 2 changed files with 76 additions and 0 deletions.
diff --git a/stan/math/rev/core/var.hpp b/stan/math/rev/core/var.hpp
@@ -7,6 +7,9 @@
 #include <boost/math/tools/config.hpp>
 #include <ostream>
 #include <vector>
+#include <complex>
+#include <string>
+#include <exception>
 
 namespace stan {
 namespace math {
@@ -179,6 +182,69 @@ class var {
   // NOLINTNEXTLINE
   var(unsigned long x) : vi_(new vari(static_cast<double>(x))) {}  // NOLINT
 
+  /**
+   * Construct a variable from the specified arithmetic argument
+   * by constructing a new <code>vari</code> with the argument
+   * cast to <code>double</code>, and a zero adjoint. Only works
+   * if the imaginary part is zero.
+   *
+   * @param x Value of the variable.
+   */
+  explicit var(const std::complex<double>& x) {
+    if (imag(x) == 0) {
+      vi_ = new vari(real(x));
+    } else {
+      std::stringstream ss;
+      ss << "Imaginary part of std::complex used to construct var"
+         << " must be zero. Found real part = " << real(x) << " and "
+         << " found imaginary part = " << imag(x) << std::endl;
+      std::string msg = ss.str();
+      throw std::invalid_argument(msg);
+    }
+  }
+
+  /**
+   * Construct a variable from the specified arithmetic argument
+   * by constructing a new <code>vari</code> with the argument
+   * cast to <code>double</code>, and a zero adjoint. Only works
+   * if the imaginary part is zero.
+   *
+   * @param x Value of the variable.
+   */
+  explicit var(const std::complex<float>& x) {
+    if (imag(x) == 0) {
+      vi_ = new vari(static_cast<double>(real(x)));
+    } else {
+      std::stringstream ss;
+      ss << "Imaginary part of std::complex used to construct var"
+         << " must be zero. Found real part = " << real(x) << " and "
+         << " found imaginary part = " << imag(x) << std::endl;
+      std::string msg = ss.str();
+      throw std::invalid_argument(msg);
+    }
+  }
+
+  /**
+   * Construct a variable from the specified arithmetic argument
+   * by constructing a new <code>vari</code> with the argument
+   * cast to <code>double</code>, and a zero adjoint. Only works
+   * if the imaginary part is zero.
+   *
+   * @param x Value of the variable.
+   */
+  explicit var(const std::complex<long double>& x) {
+    if (imag(x) == 0) {
+      vi_ = new vari(static_cast<double>(real(x)));
+    } else {
+      std::stringstream ss;
+      ss << "Imaginary part of std::complex used to construct var"
+         << " must be zero. Found real part = " << real(x) << " and "
+         << " found imaginary part = " << imag(x) << std::endl;
+      std::string msg = ss.str();
+      throw std::invalid_argument(msg);
+    }
+  }
+
 #ifdef _WIN64
 
   // these two ctors are for Win64 to enable 64-bit signed

diff --git a/test/unit/math/rev/core/var_test.cpp b/test/unit/math/rev/core/var_test.cpp
@@ -69,6 +69,16 @@ TEST_F(AgradRev, ctorOverloads) {
   // ptrdiff_t
   EXPECT_FLOAT_EQ(37, var(static_cast<ptrdiff_t>(37)).val());
   EXPECT_FLOAT_EQ(0, var(static_cast<ptrdiff_t>(0)).val());
+
+  // complex but with zero imaginary part
+  EXPECT_FLOAT_EQ(37, var(std::complex<double>(37, 0)).val());
+  EXPECT_FLOAT_EQ(37, var(std::complex<float>(37, 0)).val());
+  EXPECT_FLOAT_EQ(37, var(std::complex<long double>(37, 0)).val());
+
+  // complex but with non-zero imaginary part
+  EXPECT_THROW(var(std::complex<double>(37, 10)), std::invalid_argument);
+  EXPECT_THROW(var(std::complex<float>(37, 10)), std::invalid_argument);
+  EXPECT_THROW(var(std::complex<long double>(37, 10)), std::invalid_argument);
 }
 
 TEST_F(AgradRev, a_eq_x) {