Merge pull request #1221 from cppalliance/example_testing

Improve ADL and bit conversions examples as well as re-locate the latter

Author: mborland

doc/modules/ROOT/nav.adoc

@@ -6,7 +6,6 @@
 ** xref:examples.adoc#examples_charconv[`<charconv>`]
 ** xref:examples.adoc#examples_generic_programming[Generic Programming]
 ** xref:examples.adoc#examples_literals_constants[Literals and Constants]
-** xref:examples.adoc#examples_bit_conversions[Bit Conversions]
 ** xref:examples.adoc#examples_finance[Financial Applications]
 ** xref:examples.adoc#examples_boost_math[Boost.Math Integration]
 ** xref:examples.adoc#examples_format[Formatting]

doc/modules/ROOT/pages/conversions.adoc

@@ -9,6 +9,7 @@ https://www.boost.org/LICENSE_1_0.txt
 :idprefix: conversions_
 
 IEEE 754 specifies two different encodings for decimal floating point types: Binary Integer Significand Field (BID), and Densely Packed Decimal Significand Field (DPD).
+The former is designed for software implementations and the latter for hardware implementations.
 Internally this library is implemented in the BID format for the IEEE-754 compliant types.
 Should the user want to capture the bit format in BID or convert to DPD we offer a family of conversion functions: `to_bid`, `from_bid`, `to_dpd`, and `from_dpd` that allow conversion to or from the bit strings regardless of encoding.
 
@@ -114,3 +115,54 @@ constexpr T from_dpd(unsigned __int128 bits) noexcept;
 } // namespace decimal
 } // namespace boost
 ----
+
+== Bit Conversions Example
+
+The following example is copied and pasted from the examples/ folder of the library and is called https://github.com/cppalliance/decimal/blob/develop/examples/bit_conversions.cpp[bit_conversions.cpp].
+
+[source, c++]
+----
+#include <boost/decimal/decimal32_t.hpp>
+#include <boost/decimal/dpd_conversion.hpp>
+#include <boost/decimal/bid_conversion.hpp>
+#include <iostream>
+
+int main()
+{
+    using boost::decimal::decimal32_t;
+    using boost::decimal::from_bid;
+    using boost::decimal::from_dpd;
+    using boost::decimal::to_bid;
+    using boost::decimal::to_dpd;
+
+    // First we construct a decimal value and then convert it into both BID and DPD encoded bits
+    const decimal32_t decimal_value {5};
+    const std::uint32_t BID_bits {to_bid(decimal_value)};
+    const std::uint32_t DPD_bits {to_dpd(decimal_value)};
+
+    // Display the difference between the hex values of both bit encodings
+    std::cout << std::hex
+              << "BID format: " << BID_bits << '\n'
+              << "DPD format: " << DPD_bits << std::endl;
+
+    // Recover the original value by encoding two new decimals using the from_bid and from_dpd functions
+    const decimal32_t bid_decimal {from_bid<decimal32_t>(BID_bits)};
+    const decimal32_t dpd_decimal {from_dpd<decimal32_t>(DPD_bits)};
+
+    if (bid_decimal == dpd_decimal)
+    {
+        // These should both have recovered the original value of 5
+        return 0;
+    }
+    else
+    {
+        // Something has gone wrong recovering the decimal values
+        return 1;
+    }
+}
+----
+Output:
+----
+BID format: 32800005
+DPD format: 22500005
+----

doc/modules/ROOT/pages/examples.adoc

@@ -103,42 +103,45 @@ Returned Value: 0.25
 
 [#examples_generic_programming]
 == Generic Programming
+
+This example can be found in the `examples/` folder as https://github.com/cppalliance/decimal/blob/develop/examples/adl.cpp[adl.cpp].
+
 [source, c++]
 ----
+#include "test.hpp"
 #include <boost/decimal.hpp>
-#include <limits>
 #include <cmath>
 
-int error_counter = 0;
-
-template <typename T>
-bool float_equal(T lhs, T rhs)
-{
-    using std::fabs;
-    return fabs(lhs - rhs) < std::numeric_limits<T>::epsilon(); // numeric_limits is overloaded for all decimal types
-}
-
 template <typename T>
-void test(T val)
+void sin_identity(T val)
 {
-    using std::sin; // ADL allows builtin and decimal types to both be used
-    if (!float_equal(sin(val), -sin(-val))) // sin(x) == -sin(-x)
-    {
-        ++error_counter;
-    }
+    // ADL allows builtin and decimal types to both be used
+    // Boost.Decimal is not allowed to overload std::sin so it must be provided in its own namespace
+    // You must also include using std::sin to ensure that it is found for the float, double, and long double cases.
+    // It is preferred to have using statements for the functions you intend to use instead of using namespace XXX.
+    using std::sin;
+    using boost::decimal::sin;
+
+    // sin(x) = -sin(-x)
+    // The call here MUST be unqualified, or you will get compiler errors
+    // For example calling std::sin here would not allow any of the decimal types to be used
+    BOOST_DECIMAL_TEST_EQ(sin(val), -sin(-val));
 }
 
 int main()
 {
-    test(-0.5F);
-    test(-0.5);
-    test(-0.5L);
+    // Because of the two using statements in the above function we can now call it with built-in floating point,
+    // or our decimal types as show below
+
+    sin_identity(-0.5F);
+    sin_identity(-0.5);
+    sin_identity(-0.5L);
 
-    test(boost::decimal::decimal32_t{5, -1, true});
-    test(boost::decimal::decimal64_t{5, -1, true});
-    test(boost::decimal::decimal128_t{5, -1, true});
+    sin_identity(boost::decimal::decimal32_t{"-0.5"});
+    sin_identity(boost::decimal::decimal64_t{"-0.5"});
+    sin_identity(boost::decimal::decimal128_t{"-0.5"});
 
-    return error_counter;
+    return boost::decimal::test::report_errors();
 }
 ----
 
@@ -173,38 +176,6 @@ int main()
 }
 ----
 
-[#examples_bit_conversions]
-== Bit Conversions
-[source, c++]
-----
-#include <boost/decimal.hpp>
-#include <iostream>
-#include <iomanip>
-
-using namespace boost::decimal;
-
-int main()
-{
-    const decimal_fast32_t fast_type {5};
-    const std::uint32_t BID_bits {to_bid(fast_type)};
-    const std::uint32_t DPD_bits {to_dpd(fast_type)};
-
-    std::cout << std::hex
-              << "BID format: " << BID_bits << '\n'
-              << "DPD format: " << DPD_bits << std::endl;
-
-    const decimal32_t bid_decimal {from_bid<decimal32_t>(BID_bits)};
-    const decimal32_t dpd_decimal {from_dpd<decimal32_t>(DPD_bits)};
-
-    return !(bid_decimal == dpd_decimal);
-}
-----
-Output:
-----
-BID format: 31fc4b40
-DPD format: 35f00000
-----
-
 [#examples_finance]
 == Financial Applications
 

examples/adl.cpp

@@ -1,41 +1,44 @@
 // Copyright 2024 Matt Borland
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
+//
+// This example shows how we are able to use adl with Boost.Decimal to allow a template function
+// to use both built-in binary floating point types, as well as Boost.Decimal types
 
+#include "test.hpp"
 #include <boost/decimal.hpp>
-#include <limits>
 #include <cmath>
 
-int error_counter = 0;
-
 template <typename T>
-bool float_equal(T lhs, T rhs)
+void sin_identity(T val)
 {
-    using std::fabs;
-    return fabs(lhs - rhs) < std::numeric_limits<T>::epsilon(); // numeric_limits is overloaded for all decimal types
-}
-
-template <typename T>
-void test(T val)
-{
-    using std::sin; // ADL allows builtin and decimal types to both be used
-    if (!float_equal(sin(val), -sin(-val))) // sin(x) == -sin(-x)
-    {
-        ++error_counter;
-    }
+    // ADL allows builtin and decimal types to both be used
+    // Boost.Decimal is not allowed to overload std::sin so it must be provided in its own namespace
+    // You must also include using std::sin to ensure that it is found for the float, double, and long double cases.
+    // It is preferred to have using statements for the functions you intend to use instead of using namespace XXX.
+    using std::sin;
+    using boost::decimal::sin;
+
+    // sin(x) = -sin(-x)
+    // The call here MUST be unqualified, or you will get compiler errors
+    // For example calling std::sin here would not allow any of the decimal types to be used
+    BOOST_DECIMAL_TEST_EQ(sin(val), -sin(-val));
 }
 
 int main()
 {
-    test(-0.5F);
-    test(-0.5);
-    test(-0.5L);
-
-    test(boost::decimal::decimal32_t{-5, -1});
-    test(boost::decimal::decimal64_t{-5, -1});
-    test(boost::decimal::decimal128_t{-5, -1});
-
-    return error_counter;
+    // Because of the two using statements in the above function we can now call it with built-in floating point,
+    // or our decimal types as show below
+        
+    sin_identity(-0.5F);
+    sin_identity(-0.5);
+    sin_identity(-0.5L);
+
+    sin_identity(boost::decimal::decimal32_t{"-0.5"});
+    sin_identity(boost::decimal::decimal64_t{"-0.5"});
+    sin_identity(boost::decimal::decimal128_t{"-0.5"});
+
+    return boost::decimal::test::report_errors();
 }
 
 

examples/bit_conversions.cpp

@@ -2,24 +2,41 @@
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
 
-#include <boost/decimal.hpp>
+#include <boost/decimal/decimal32_t.hpp>
+#include <boost/decimal/dpd_conversion.hpp>
+#include <boost/decimal/bid_conversion.hpp>
 #include <iostream>
-#include <iomanip>
-
-using namespace boost::decimal;
 
 int main()
 {
-    const decimal_fast32_t fast_type {5};
-    const std::uint32_t BID_bits {to_bid(fast_type)};
-    const std::uint32_t DPD_bits {to_dpd(fast_type)};
+    using boost::decimal::decimal32_t;
+    using boost::decimal::from_bid;
+    using boost::decimal::from_dpd;
+    using boost::decimal::to_bid;
+    using boost::decimal::to_dpd;
+
+    // First we construct a decimal value and then convert it into both BID and DPD encoded bits
+    const decimal32_t decimal_value {5};
+    const std::uint32_t BID_bits {to_bid(decimal_value)};
+    const std::uint32_t DPD_bits {to_dpd(decimal_value)};
 
+    // Display the difference between the hex values of both bit encodings
     std::cout << std::hex
               << "BID format: " << BID_bits << '\n'
               << "DPD format: " << DPD_bits << std::endl;
 
+    // Recover the original value by encoding two new decimals using the from_bid and from_dpd functions
     const decimal32_t bid_decimal {from_bid<decimal32_t>(BID_bits)};
     const decimal32_t dpd_decimal {from_dpd<decimal32_t>(DPD_bits)};
 
-    return !(bid_decimal == dpd_decimal);
+    if (bid_decimal == dpd_decimal)
+    {
+        // These should both have recovered the original value of 5
+        return 0;
+    }
+    else
+    {
+        // Something has gone wrong recovering the decimal values
+        return 1;
+    }
 }

examples/test.hpp

@@ -0,0 +1,63 @@
+// Copyright 2025 Matt Borland
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+//
+// Some trivial testing facilities so that the library examples can run without boost
+// Running the full test suite in the test/ directory does require boost
+
+#ifndef BOOST_DECIMAL_EXAMPLES_TEST_HPP
+#define BOOST_DECIMAL_EXAMPLES_TEST_HPP
+
+#include <boost/decimal/iostream.hpp>
+#include <iostream>
+#include <type_traits>
+#include <limits>
+
+namespace boost {
+namespace decimal {
+namespace test {
+
+static int errors = 0;
+
+inline int report_errors()
+{
+    // Limited on the upper bound of main return on some platforms
+    return errors > 255 ? 255 : errors;
+}
+
+inline void test(const bool x)
+{
+    if (!x)
+    {
+        ++errors;
+        std::cerr << "Test Failed at line: " << __LINE__ << std::endl;
+    }
+}
+
+template <typename T, std::enable_if_t<!std::is_floating_point<T>::value, bool> = true>
+void test_eq(const T lhs, const T rhs)
+{
+    if (lhs != rhs)
+    {
+        ++errors;
+        std::cerr << "Failed equality test for: " << lhs << " and " << rhs << " at line: " << __LINE__ << std::endl;
+    }
+}
+
+template <typename T, std::enable_if_t<std::is_floating_point<T>::value, bool> = true>
+void test_eq(const T a, const T b)
+{
+    // Knuth's approximate float equality from The Art of Computer Programming
+    // See also: https://stackoverflow.com/questions/17333/how-do-you-compare-float-and-double-while-accounting-for-precision-loss
+    using std::fabs;
+    test(fabs(a - b) <= ((fabs(a) < fabs(b) ? fabs(b) : fabs(a)) * std::numeric_limits<T>::epsilon()));
+}
+
+} // namespace test
+} // namespace decimal
+} // namespace boost
+
+#define BOOST_DECIMAL_TEST(x) boost::decimal::test::test(x);
+#define BOOST_DECIMAL_TEST_EQ(lhs, rhs) boost::decimal::test::test_eq(lhs, rhs)
+
+#endif // BOOST_DECIMAL_EXAMPLES_TEST_HPP