C++ – How to use the features of C++ to make cleaner use of i18n library over direct use of gettext() with C

cgettextinternationalization

I would like to have an easy to use way to write code like:

#include <iostream>
int main (){
    std::cout << "hello, world!\n";
}

but that supports i18n. Here is an example using gettext():

#include <libintl.h>
#include <iostream>
int main (){
    std::cout << gettext("hello, world!\n");
}

This can then be processed by xgettext to produce a message catalog file that can be used
by translators to create various versions. These extra files can be handled on target
systems to allow the user to interact in a preferred language.

I would like to write the code something like this instead:

#include <i18n-iostream>
int main (){
    i18n::cout << "hello, world!\n";
}

At build time the quoted strings would be examined by a program like xgettext to produce the
base message catalog file. << operator with argument i18n::cout would take a string
literal as the key to lookup the run-time text to use from a message catalog.

Does it exist somewhere?

Best Answer

At build time the quoted strings would be examined by a program like xgettext to produce the base message catalog file. << operator with argument i18n::cout would take a string literal as the key to lookup the run-time text to use from a message catalog.

You try to convert a string like a single instance, but it isn't/

The point, you don't want something like this. Think of:

if(n=1)
    i18n::cout << "I need one apple"
else
    i18n::cout << "I need " << n << " apples" ;

So why this is would not work, because "n=1" or "n!=1" works only for English, many other languages have more then one plural form, also it requires translation of "I need X apples" as signle instance.

I suggest you just to learn to deal with gettext, it is quite simple and powerful, many people had thought about it.

Another point, you are usually do not call gettext but

#include <libintl.h>
#include <iostream>
#define _(x) gettext(x)

int main (){
    std::cout << _("hello, world!\n");
}

This makes the code much cleaner, also it is quite a "standard" feature to use "_" as gettext alias.

Just learn how to use it, before you try to make "nicer" API. Just to mention, gettext API is quite de-facto standard for many languages, not only C.

Related Solutions

C++ – How to iterate over the words of a string

I use this to split string by a delimiter. The first puts the results in a pre-constructed vector, the second returns a new vector.

#include <string>
#include <sstream>
#include <vector>
#include <iterator>

template <typename Out>
void split(const std::string &s, char delim, Out result) {
    std::istringstream iss(s);
    std::string item;
    while (std::getline(iss, item, delim)) {
        *result++ = item;
    }
}

std::vector<std::string> split(const std::string &s, char delim) {
    std::vector<std::string> elems;
    split(s, delim, std::back_inserter(elems));
    return elems;
}

Note that this solution does not skip empty tokens, so the following will find 4 items, one of which is empty:

std::vector<std::string> x = split("one:two::three", ':');

C++ – Do the parentheses after the type name make a difference with new

Let's get pedantic, because there are differences that can actually affect your code's behavior. Much of the following is taken from comments made to an "Old New Thing" article.

Sometimes the memory returned by the new operator will be initialized, and sometimes it won't depending on whether the type you're newing up is a POD (plain old data), or if it's a class that contains POD members and is using a compiler-generated default constructor.

In C++1998 there are 2 types of initialization: zero and default
In C++2003 a 3rd type of initialization, value initialization was added.

Assume:

struct A { int m; }; // POD
struct B { ~B(); int m; }; // non-POD, compiler generated default ctor
struct C { C() : m() {}; ~C(); int m; }; // non-POD, default-initialising m

In a C++98 compiler, the following should occur:

new A - indeterminate value
new A() - zero-initialize
new B - default construct (B::m is uninitialized)
new B() - default construct (B::m is uninitialized)
new C - default construct (C::m is zero-initialized)
new C() - default construct (C::m is zero-initialized)

In a C++03 conformant compiler, things should work like so:

new A - indeterminate value
new A() - value-initialize A, which is zero-initialization since it's a POD.
new B - default-initializes (leaves B::m uninitialized)
new B() - value-initializes B which zero-initializes all fields since its default ctor is compiler generated as opposed to user-defined.
new C - default-initializes C, which calls the default ctor.
new C() - value-initializes C, which calls the default ctor.

So in all versions of C++ there's a difference between new A and new A() because A is a POD.

And there's a difference in behavior between C++98 and C++03 for the case new B().

This is one of the dusty corners of C++ that can drive you crazy. When constructing an object, sometimes you want/need the parens, sometimes you absolutely cannot have them, and sometimes it doesn't matter.

Best Answer

Related Solutions

C++ – How to iterate over the words of a string

C++ – Do the parentheses after the type name make a difference with new

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