Io

module file_io(buf,name) = {

    action read(fname:name, b:buf) returns (b:buf, ok : bool) = {

        <<<

        std::string fn;
        for (size_t i = 0; i < fname.size(); i++)
            fn.push_back(fname[i]);
        int fd = ::open(fn.c_str(),0);
        if (fd < 0) {
            ok = false;
        } else {
            std::vector<char> tmp;
            tmp.resize(2048);
            int len;
            while ((len = ::read(fd,&tmp[0],2048)) > 0) {
                for (size_t i = 0; i < len; i++)
                    b.push_back(tmp[i]);
            }
            ok = (len >= 0);
            ::close(fd);
        }
        >>>
    }

    action write(fname:name, b:buf) returns (ok : bool) = {

        <<<

        std::string fn;
        for (size_t i = 0; i < fname.size(); i++)
            fn.push_back(fname[i]);
        int fd = ::creat(fn.c_str(),0660);
        if (fd < 0) {
            ok = false;
        } else {
            std::vector<char> tmp;
            tmp.resize(b.size());
            for (size_t i = 0; i < tmp.size(); i++) {
                tmp[i] = b[i];
            }
            ssize_t bytes = ::write(fd,&tmp[0],tmp.size());
            ok = (bytes == tmp.size());
            ::close(fd);
        }
        >>>
    }


    action exist(fname:name) returns (ok : bool) = {

        <<<

        std::string fn;
        for (size_t i = 0; i < fname.size(); i++)
        fn.push_back(fname[i]);
        ok = ::access(fn.c_str(),F_OK) != -1;

        >>>
    }


}

module path_name(name) = {
    action change_extension(path:name,ext:name) returns (path:name) = {
        if path.end > 0 {
            var idx := path.end.prev;
            while idx > 0 & path.value(idx) ~= 46 {  # dot
                idx := idx.prev;
            };
            if path.value(idx) = 46 {
                path := path.segment(path.begin,idx);
                path := path.extend(".");
                path := path.extend(ext)
            }
        }
    }

    action concat(path1:name,path2:name) returns (path1:name) = {
        path1 := path1.extend("/");
        path1 := path1.extend(path2);
    }
}

The stdio module provides input/output on the standard streams, that is, standard input, standard output and standard error. It takes a parameter str, which is a type with string traits.

module io_stdio(str,domain,range) = {

The write action writes a string to standard output.

        action write(s:str) = {
    <<<
    for (unsigned i = 0; i < s.size(); i++) {
        std::cout.put(s[i]);
        }
    >>>
    }

The write action writes a string to standard output followed by newline.

        action writeln(s:str) = {
    <<<
    for (unsigned i = 0; i < s.size(); i++) {
        std::cout.put(s[i]);
        }
    std::cout.put(10);
    >>>
        }

The read action from standard input untio EOF.

        action read returns (s:str) = {
    <<<
    int c = std::cin.get();
        while (c >= 0) {
            s.push_back(c);
        c = std::cin.get();
        }
    >>>
        }

The readln action reads a line from standard input, returning the line without any terminating newline character.

        action readln returns (s:str) = {
    <<<
    int c = std::cin.get();
        while (c >= 0 && c != 10) {
            s.push_back(c);
        c = std::cin.get();
        }
    >>>
    }
}