scan
Musings on a C++ version of scanf.
sscanr
int sscanr(std::string\_view input, const std::regex& re, ...);
I wrote that as if it were a C-style variadic function, but it is really a C++ variadic template function.
This function matches input against re. For each submatch, it uses operator>> to parse the submatch and assign its value to the next argument.
It returns the number of arguments that it assigned values to.
For example:
std::regex re{"([^:]+) *: *([0-9]+)"};
std::string name;
int value{0};
int count = sscanr("total: 15", re, name, value);
std::cout << count << '\n';
std::cout << name << '\n';
std::cout << value << '\n';
...would output...
2
total
15
scanr
Ideally there would be a scanr function like this...
int scanr(std::istream& input, const std::regex& re, ...);
...but std::regex_match doesn't play nice with std::istream. Sigh
This can be worked around, but I haven't done it yet.
scan
This is a work-in-progress.
int scan(std::istream& input, std::string\_view format, ...);
Again...not a C variadic function but a C++ variadic function template.
This function aims to be mostly like scanf (or, I suppose, fscanf), but...
- It takes a std::istream& instead of a FILE* for the input
- It takes a std::string_view instead of a const char* for the format
- It knows the types of the additional arguments
- It ignores the "length modifier" part of any conversion specifiers since it knows the type of the corresponding argument
There is also this overload...
int scan(std::string\_view format, ...);
...which reads from std::cin.
sscan
int sscan(std::string\_view input, std::string\_view format, ...);
Like scan, but reads from a std::string_view instead of a std::istream&.