This question already has answers here:
Handling large numbers in C++?
(10 answers)
Closed 8 years ago.
Is it possible to take an input of range greater than what C/C++ provides? Is it possible to accept an input range greater than that of unsigned long long and even larger up to the range of 10^1000?
If it is possible in C/C++, please answer how it can be done, thanks.
There's no bigint in C or C++, however library like this one can provide it: https://code.google.com/p/infint/
Input into a string. Then convert the string into the desired type.
If you use a library that provides types for large integers, such a library might also offer input functions.
Related
This question already has answers here:
What does the C++ standard state the size of int, long type to be?
(24 answers)
Getting the actual length of a UTF-8 encoded std::string?
(11 answers)
Closed 2 years ago.
I was reading the documentation of string::length and, as you can see, it says that
Returns the length of the string, in terms of bytes.
So my question is, is this ensured to be also the number of char that it contains?
I know that usually a char is 1 byte, but is this ensured somewhere? Like in the standard or somewhere else?
This question already has answers here:
Turn off scientific notation on float
(2 answers)
Closed 2 years ago.
I'm currently coding a project for my Computer Science module but I'm having the problem of my string value defaulting to scientific notation if there are too many decimal places in the double value.
I've tried the obvious solution with ostringstream and .str() but it makes it into notation. I have to compile to the C++98 standard, so I cannot use modern solutions like std::to_string.
I need the value to be casted into a string but it needs to maintain its formatting. any help would be appreciated.
I would use:
std::to_string(myDouble);
If you use at least C++17, you could use std::to_chars() from #include <charconv>.
// `512` is here arbitrary, it is the max size of the output string.
// Smaller values should be sufficient.
char buffer[512];
// Here 'std::chars_format::fixed' tells the `std::to_chars()` to
// not use the scientific notation.
char* end = std::to_chars(std::begin(buffer), std::end(buffer), myDouble, std::chars_format::fixed).ptr;
// `end` the one-past-the-end pointer of the characters written to `buffer`.
This method is probably faster than the Emilien Lemaire's answer, however it's more verbose, and more error-prone. So this answer is only provided for completeness (as the performance gain may not worth it).
Moreover, unlike std::to_string(), the output string is locale-insensitive, so the double will always be formatted in the C locale (english locale).
This question already has answers here:
How to determine if a string is a number with C++?
(36 answers)
How to convert a command-line argument to int?
(8 answers)
Closed 9 years ago.
I want to validate the input by user to make sure it's an integer (fully). I've tried a few methods, like !cin, but none of them work properly..
Most of methods fail to validate input like this:
32tgf
When there is a number first and then letters, it doesn't fail, but it takes it as valid entry..
Note: It's a project for college and it's specified that the variable should be of type int.
Read into a string, then use e.g. std::stoi or std::strtol to both convert to an integer and validate the input.
Or read into a string, put that string in a std::istringstream which you use to extract the integer. Then check if there's anything more in the istringstream.
I'd recommend the first method though.
This question already has answers here:
Closed 12 years ago.
Possible Duplicate:
Maximum length of a std::basic_string<_CharT> string
I would like to know how many characters does string class in c++ support.
thanks..
std::string s;
s.max_size();
That should tell you what that max size is.
according to http://www.idinews.com/string3.html
The std::string class supports varying length strings with no length limit.
I am lead to believe that the size of a std::string object is limited to size of an unsigned integer on the architecture of your system. I would assume this since the length of the string is stored as a size_t value.
This question already has answers here:
Closed 12 years ago.
Possible Duplicate:
Is it possible to define enumalpha?
Is there any equivalent of Java Enum.valueOf(string) on C++?
There's no table of names generated by the compiler (unless you count debug information), but if you create one (or use e.g. doxygen which parses the source code and can output such lists in XML format) then you can use a dictionary of some type, such as std::map<string, int> to turn an identifier into its numeric value.
No, there isn't even the much simpler task of going the other way (enum to string), you'd need to write it yourself