鉴于 Boost.Program_Options 的以下简单使用:
boost::program_options::options_description options("Options");
options.add_options()
("my_bool_flag,b", boost::program_options::value<bool>(), "Sample boolean switch)")
;
...哪些命令行参数将评估为 false
,哪些评估为 true
?
(即假设程序名为“foo”,并在命令行上执行为:
foo -b ?
...问号是其他一些文本的占位符:所有可能的文本选项将正确评估为 false
,什么是 true
?)
最佳答案
查看 $(BOOST_ROOT)/libs/program_options/src/value_semantic.cpp 你可以发现:
/* Validates bool value.
Any of "1", "true", "yes", "on" will be converted to "1".<br>
Any of "0", "false", "no", "off" will be converted to "0".<br>
Case is ignored. The 'xs' vector can either be empty, in which
case the value is 'true', or can contain explicit value.
*/
BOOST_PROGRAM_OPTIONS_DECL void validate(any& v, const vector<string>& xs,
bool*, int)
{
check_first_occurrence(v);
string s(get_single_string(xs, true));
for (size_t i = 0; i < s.size(); ++i)
s[i] = char(tolower(s[i]));
if (s.empty() || s == "on" || s == "yes" || s == "1" || s == "true")
v = any(true);
else if (s == "off" || s == "no" || s == "0" || s == "false")
v = any(false);
else
boost::throw_exception(invalid_bool_value(s));
}
关于c++ - Boost.Program_Options : When <bool> is specified as a command-line option, 什么是有效的命令行参数?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/15629771/