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After some time implementing my own streambuf I askes myself if you can use different types for the basic_streambuf like double. Are there any experiences and use cases here?
You're missing the point of streambuf. It's the back end of std::stream. The front end is provided by operator<< and operator>>. Those are overloaded for double. The frond end converts any type to characters, the back end does the I/O (to file, screen, network, whatever)
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I am looking for a function to compare the two strings. A functional similar to strcmp in CString with the difference that takes two strands in the input.
You can use std::string::compare (it returns 0 if values are the same). Also be aware that in fact you can use strcmp in c++, but if you want modern c++ version i would go with std::string::compare.
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I'd like to know if there is a way to transform a string into a function em c++. For example if I have the string: "x+y" it'd create the function and by replacing x and y, get the value of it.
In Java there is this API https://www.objecthunter.net/exp4j/index.html, so I was wondering if there is something similar.
There are many possible methods one could use to transform a string into a "function". Many of those involve parsing the string and building a function-like object out of it.
A lightweight and portable solution would be to use ExprTk, a mathematical expression library developed by Arash Partow.
The main page contains various usage examples.
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A simple example of how you would structure this would be particularly useful.
This is how I would do it:
MyMotor is an instance of the class Motor. This class has four functions idle(), accelerate(), flat(), decelerate(). (I assume you know how to build a basic class with private members and its constructors)
Then in main(), I create MyMotor and control it based on states. States can be controlled/monitored using Boolean Values. Whatever state I am in and whenever, certain function will be called.
Next time give it a try before you ask here, in order to get better responses.
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I've tried searching for the answer, but nothing mentions stringstream specifically. I would guess that it would always work and you can always go back as far as the beginning of the underlying string.
Am I right?
How likely is istream::ungetc() to work with a stringbuf (as used in stringstream)?
Well, never.
There's no such thing like istream::ungetc() defined from the standard.
You can use either
int std::ungetc( int ch, std::FILE *stream )
or
std::basic_istream& std::basic_istream::unget()
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I would like to be able to convert a string such as "(5+6)*6" and get the resulting integer from that equation. It is important that it starts out as a string.
You can use library fastmathparser for c++.
In link is example how use this library.
If you really want write alone this parser, I recomended use Shunting-yard algorithm