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Support scientific notation for floating point

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This commit is contained in:
Glen Fraser
2015-04-29 19:40:58 +02:00
parent 86ec14c2c8
commit d762ef08b6
2 changed files with 50 additions and 8 deletions
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46
include/chaiscript/language/chaiscript_parser.hpp
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@@ -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;