From 40123e7170713d33945b472dfeaf73d485af67e7 Mon Sep 17 00:00:00 2001
From: John Maddock <john@johnmaddock.co.uk>
Date: Tue, 22 Nov 2011 09:51:58 +0000
Subject: [PATCH] Change number formatting when std::ios_base::fixed is set to
 print the requested number of digits, padding with zeros as required.

[SVN r75602]
---
 include/boost/multiprecision/cpp_float.hpp |  8 ++++++
 include/boost/multiprecision/gmp.hpp       | 27 ++++++++++++------
 include/boost/multiprecision/mpfr.hpp      | 32 +++++++++++++---------
 3 files changed, 45 insertions(+), 22 deletions(-)

diff --git a/include/boost/multiprecision/cpp_float.hpp b/include/boost/multiprecision/cpp_float.hpp
index 51b0eb95..41ad3005 100644
--- a/include/boost/multiprecision/cpp_float.hpp
+++ b/include/boost/multiprecision/cpp_float.hpp
@@ -1755,6 +1755,14 @@ std::string cpp_float<Digits10>::str(std::streamsize number_of_digits, std::ios_
       str.append(1, 'e');
       str.append(boost::lexical_cast<std::string>(my_exp));
    }
+   if(showpoint || scientific)
+   {
+      std::streamsize chars = str.size() - 1;
+      BOOST_ASSERT(str.find('.') != std::string::npos); // there must be a decimal point!!
+      chars = number_of_digits - chars;
+      if(chars > 0)
+         str.append(chars, '0');
+   }
    if(isneg())
       str.insert(0, 1, '-');
    else if(shopos)
diff --git a/include/boost/multiprecision/gmp.hpp b/include/boost/multiprecision/gmp.hpp
index 7faa4b58..150782cb 100644
--- a/include/boost/multiprecision/gmp.hpp
+++ b/include/boost/multiprecision/gmp.hpp
@@ -173,17 +173,14 @@ struct gmp_float_imp
       void (*free_func_ptr) (void *, size_t);
       const char* ps = mpf_get_str (0, &e, 10, static_cast<std::size_t>(digits), m_data);
       std::ptrdiff_t sl = std::strlen(ps);
+      if(ps && *ps == '-')
+         --sl; // number of digits excluding sign.
+      result = ps;
       if(sl == 0)
       {
          result = scientific ? "0.0e0" : showpoint ? "0.0" : "0";
-         if(showpos)
-            result.insert(0, 1, '+');
-         return "0";
       }
-      if(*ps == '-')
-         --sl; // number of digits excluding sign.
-      result = ps;
-      if(fixed || (!scientific && (e > -4) && (e <= std::numeric_limits<boost::uintmax_t>::digits10 + 2)))
+      else if(fixed || (!scientific && (e > -4) && (e <= std::numeric_limits<boost::uintmax_t>::digits10 + 2)))
       {
          if(1 + e >= sl)
          {
@@ -215,8 +212,20 @@ struct gmp_float_imp
          if(e)
             result += "e" + lexical_cast<std::string>(e);
       }
-      if(shopos && (str[0] != '-'))
-         str.insert(0, 1, '+');
+      if(showpoint || scientific)
+      {
+         // Pad out end with zeros as required to give required precision.
+         std::streamsize chars = result.size() - 1;
+         BOOST_ASSERT(result.find('.') != std::string::npos); // there must be a decimal point!!
+         BOOST_ASSERT(result.size()); // Better not be a null string by this point!!
+         if(result[0] == '-')
+            --chars;
+         chars = digits - chars;
+         if(chars > 0)
+            result.append(static_cast<std::string::size_type>(chars), '0');
+      }
+      if(showpos && (result[0] != '-'))
+         result.insert(0, 1, '+');
       mp_get_memory_functions(&alloc_func_ptr, &realloc_func_ptr, &free_func_ptr);
       (*free_func_ptr)((void*)ps, std::strlen(ps) + 1);
       return result;
diff --git a/include/boost/multiprecision/mpfr.hpp b/include/boost/multiprecision/mpfr.hpp
index 22c2f3f9..2fbae2c8 100644
--- a/include/boost/multiprecision/mpfr.hpp
+++ b/include/boost/multiprecision/mpfr.hpp
@@ -168,21 +168,15 @@ struct mpfr_float_imp
       char* ps = mpfr_get_str (0, &e, 10, static_cast<std::size_t>(digits), m_data, GMP_RNDN);
       std::ptrdiff_t sl = std::strlen(ps);
       int chars = sl;
-      if(sl == 0)
-      {
-         result = scientific ? "0.0e0" : showpoint ? "0.0" : "0";
-         if(showpos)
-            result.insert(0, 1, '+');
-         return "0";
-      }
-      while(ps[chars-1] == '0')
+      while(chars && (ps[chars-1] == '0'))
          --chars;
       ps[chars] = 0;
-      if(*ps == '-')
+      if(chars && (*ps == '-'))
          --chars; // number of digits excluding sign.
       if(chars == 0)
-         return scientific ? "0.0e0" : showpoint ? "0.0" : "0";
-      result = ps;
+         result = "0";
+      else
+         result = ps;
       if(fixed || (!scientific && (e > -4) && (e <= std::numeric_limits<boost::uintmax_t>::digits10 + 2)))
       {
          if(e >= chars)
@@ -215,8 +209,20 @@ struct mpfr_float_imp
          if(e)
             result += "e" + lexical_cast<std::string>(e);
       }
-      if(shopos && (str[0] != '-'))
-         str.insert(0, 1, '+');
+      if(showpoint || scientific)
+      {
+         // Pad out end with zeros as required to give required precision.
+         std::streamsize chars = result.size() - 1;
+         BOOST_ASSERT(result.find('.') != std::string::npos); // there must be a decimal point!!
+         BOOST_ASSERT(result.size()); // Better not be a null string by this point!!
+         if(result[0] == '-')
+            --chars;
+         chars = digits - chars;
+         if(chars > 0)
+            result.append(static_cast<std::string::size_type>(chars), '0');
+      }
+      if(showpos && (result[0] != '-'))
+         result.insert(0, 1, '+');
       mpfr_free_str(ps);
       return result;
    }