From d762ef08b6d70f2382d9a1ccf5c3c2fed2603c57 Mon Sep 17 00:00:00 2001
From: Glen Fraser <holaglen@gmail.com>
Date: Wed, 29 Apr 2015 19:40:58 +0200
Subject: [PATCH 1/2] Support scientific notation for floating point

---
 .../chaiscript/language/chaiscript_parser.hpp | 46 +++++++++++++++----
 unittests/float.chai                          | 12 +++++
 2 files changed, 50 insertions(+), 8 deletions(-)

diff --git a/include/chaiscript/language/chaiscript_parser.hpp b/include/chaiscript/language/chaiscript_parser.hpp
index 5245b20..32c24bf 100644
--- a/include/chaiscript/language/chaiscript_parser.hpp
+++ b/include/chaiscript/language/chaiscript_parser.hpp
@@ -423,6 +423,37 @@ namespace chaiscript
         return retval;
       }
 
+      /// Reads the optional exponent (scientific notation) and suffix for a Float
+      bool read_exponent_and_suffix() {
+        // Support a form of scientific notation: 1e-5, 35.5E+8, 0.01e19
+        if (has_more_input() && (std::tolower(*m_input_pos) == 'e')) {
+          ++m_input_pos;
+          ++m_col;
+          if (has_more_input() && ((*m_input_pos == '-') || (*m_input_pos == '+'))) {
+            ++m_input_pos;
+            ++m_col;
+          }
+          auto exponent_pos = m_input_pos;
+          while (has_more_input() && char_in_alphabet(*m_input_pos,detail::int_alphabet) ) {
+            ++m_input_pos;
+            ++m_col;
+          }
+          if (m_input_pos == exponent_pos) {
+            // Require at least one digit after the exponent
+            return false;
+          }
+        }
+
+        // Parse optional float suffix
+        while (has_more_input() && char_in_alphabet(*m_input_pos, detail::float_suffix_alphabet))
+        {
+          ++m_input_pos;
+          ++m_col;
+        }
+
+        return true;
+      }
+
 
       /// Reads a floating point value from input, without skipping initial whitespace
       bool Float_() {
@@ -432,7 +463,11 @@ namespace chaiscript
             ++m_col;
           }
 
-          if (has_more_input() && (*m_input_pos == '.')) {
+          if (has_more_input() && (std::tolower(*m_input_pos) == 'e')) {
+            // The exponent is valid even without any decimal in the Float (1e8, 3e-15)
+            return read_exponent_and_suffix();
+          }
+          else if (has_more_input() && (*m_input_pos == '.')) {
             ++m_input_pos;
             ++m_col;
             if (has_more_input() && char_in_alphabet(*m_input_pos,detail::int_alphabet)) {
@@ -441,13 +476,8 @@ namespace chaiscript
                 ++m_col;
               }
 
-              while (has_more_input() && char_in_alphabet(*m_input_pos, detail::float_suffix_alphabet))
-              {
-                ++m_input_pos;
-                ++m_col;
-              }
-
-              return true;
+              // After any decimal digits, support an optional exponent (3.7e3)
+              return read_exponent_and_suffix();
             } else {
               --m_input_pos;
               --m_col;
diff --git a/unittests/float.chai b/unittests/float.chai
index b1bdf29..9a76aa3 100644
--- a/unittests/float.chai
+++ b/unittests/float.chai
@@ -5,3 +5,15 @@ assert_equal(1.2, 1.2)
 assert_equal(true, .5 > 0)
 assert_equal(true, .5 < 1)
 assert_equal(0.5, .5)
+
+// Scientific notation tests
+assert_equal(to_string(-1.7e30f), "-1.7e+30")
+assert_equal(to_string(+17.9E04), "179000")
+assert_equal(to_string(-1.7e+300), "-1.7e+300")
+assert_equal(to_string(-1.7e-300), "-1.7e-300")
+assert_equal(to_string(17.5e30l), "1.75e+31")
+assert_equal(to_string(1/3.14159e300L), "3.1831e-301")
+assert_equal(to_string(1.0 / 12345), "8.10045e-05")
+assert_equal(to_string(3e8F), "3e+08")
+assert_equal(to_string(-15E-8*3e8), "-45")
+assert_equal(to_string(-0.5e+3+20e-01), "-498")

From 8fc61bf51c184ce0eb6c5d71521b83f92a930036 Mon Sep 17 00:00:00 2001
From: Glen Fraser <holaglen@gmail.com>
Date: Wed, 29 Apr 2015 21:52:34 +0200
Subject: [PATCH 2/2] Fixing build error with tolower() on Windows

---
 include/chaiscript/language/chaiscript_parser.hpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/chaiscript/language/chaiscript_parser.hpp b/include/chaiscript/language/chaiscript_parser.hpp
index 32c24bf..1acb4f1 100644
--- a/include/chaiscript/language/chaiscript_parser.hpp
+++ b/include/chaiscript/language/chaiscript_parser.hpp
@@ -16,6 +16,7 @@
 #include <sstream>
 #include <string>
 #include <vector>
+#include <cctype>
 
 #include "../dispatchkit/boxed_value.hpp"
 #include "chaiscript_common.hpp"