ConstexprString

The library consists of a small string class which allows for compile time string manipulations like eg concatenation.

The library

• comes in a single header file, is
• macro-free,
• depency-free,
• tested under GCC 7.2.0
• Compiles under GCC 5.1-8.1, ICC 17-18, Clang 3.5-6.0
• The abstraction will be fully optimized out at optimization Level 2 (-O2)

Motivation

On the day to day work one often comes across definitions like

#define TMP_DIR "/tmp"
#define TMP_FILE_1 TMP_DIR "/file1"
#define TMP_FILE_2 TMP_DIR "/file2"

where macro based string definitions allow the user to combine c-strings to form new ones. Since macros are best to be avoided one needs a comparable mechanism on the c++ language level.

This library provides such a mechanism which allows us to rewrite the example above without macros:

constexpr auto TMP_DIR = ces::make_string("/tmp");
constexpr auto TMP_FILE_1 = TMP_DIR + "/file1";
constexpr auto TMP_FILE_2 = TMP_DIR + "/file2";

Working Example

#include "ConstexprString.h"


constexpr char foo[] = "foo";
constexpr char bar[] = "bar";
constexpr auto foobar = ces::make_string(foo) + " " + bar;

int main_()
{
    std::cout << foobar << std::endl; //prints "foo bar"
    return 0;
}

Try it out on ideone.

How the example works

The call to function ces::make_string(foo) returns an instance of ces::ConstexprString which contains a copy of the argument foo and for which an appropriate operator+() is provided for the subequent calls +" " + bar.

Note

This library provides only a limited set of compile time string operations. For a more complete set one can use other compile-time libraries like sprout.