© Ali AlSaibie, PhD.
© Ali AlSaibie, PhD.
Recall the cmath or iostream or stdint or bitset headers? These are actually part of what is called the standard library, which contains a number of useful extension functionalities to C/C++.
As you probably have realized. The bare functionalities of C/C++ are quite limited. There aren’t many built-in functions.
When you need additional functions you include the relevant sources. This makes sense, since C/C++ strive to be efficient compiled languages and why include things that are not needed?
There are a lot of libraries out there for C/C++, so what is special about the standard library? Well, for one they are standard, they are supported and updated by the languages’ standards committees. This ensures consistency and uniformity in the language application. They can be thought of as part of the language as well.
It is worth noting that as of this writing, the latest C programming standard is C17 (from 2017) and the latest C++ standard is C++20 (2020). There is a lot more enhancement and modernization activity in the C++ space compared to C.
C++ implementations that leverage the major changes from 2011 are referred to as Modern C++, but that description will drop with time of course.
As engineers we are likely to implement some math functions in our code. The math library contains a set of common functions. Functions such sine cosine power square root, logs and exponentials. And a host of other functions.
There are several resources online that list all the functionalities of the standard libraries such as cplusplus.com & cppreference.com.
Note that, if coming from MATLAB, you are probably used to manipulating matrices out of the box. There are no built in matrix library in C/C++. In C++ there are several third party libraries and one commonly used is Eigen.
When you want to store, iterate and manipulate a sequence of items, be it variables, including pointers to functions, classes and other elements. You can use vectors.
These are not mathematical vectors. They are similar to arrays in that they store elements in a contiguous storage location, but unlike arrays, they are dynamically sized.
While the program is running you can shift, iterate, insert, swap, pop from the vector. And these functionalities are built into the vector container. As you would expect, vectors consume more memory compared to arrays.
The iostream defines the basic input/output interface functions.
We have seen how cout is used to print characters and numbers to the terminal. We can use cin to read characters in from the terminal via the keyboard.
There is also clog which outputs characters for logging and cerr for errors, these can be routed to different locations. The log outputs may be routed to a log file and the error may be formatted in the output with a different color.
#include <cstdint>
#include <iostream>
int main(int argc, char *argv[]){
uint8_t c;
std::cin >> c;
std::cout << c << std::endl; /* Outputs inputted character */
return 1;
}An essential standard library is the cstdint library. It actually might be indirectly included if you include other standard library headers. This varies and depends on the platform you are working on.
<cstdint> Defines a set of integral type aliases with specific width requirements, such as:
uint8_t: unsigned integer of 1 byte size
int16_t: signed integer of 2 byte size
intmax_t: signed integer of max size supported on platform
uint_least32_t: unsigned of at least 4 bytes
int_fast8_t: At least as fast as any other type of at least 1 byte size
int8_t may not be the faster in math ops than int16_t for instance, as higher bit CPUs need extra steps to work with partial register size data
For basic embedded applications, it is safe to use standard types, then optimize if needed
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