http://d.puremagic.com/issues/show_bug.cgi?id=4716

           Summary: std.stdio.input() or similar
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2010-08-22 20:02:39 PDT ---
If not already present, a function template similar to this one may be useful for the std.stdio module. Similar functions are present in Basic and Python languages:


T input(T)(string msg) {
    write(msg);
    auto read = readln();
    static if (!is(T == string) && !is(T == dstring) &&!is(T == wstring))
        read = read.strip();
    return to!T(read);
}


To be used mostly in scripts, as:

double x = input!double("Enter value x: ");

Its name may be changed if there is collision with something different, but it needs to be simple, given its purpose.

This function may be made much more refined, but I suggest to keep it simple. Even the static if it contains is more complex than originally thought.

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--- Comment #1 from bearophile_hugs@eml.cc 2010-08-23 05:14:22 PDT ---
Improved code. Both IsType() and IsString() may be useful to add to std.traits,
if something similar is not already present.


import std.string: chomp;
import std.stdio: write, readln;
import std.conv: to;

// true is T is one of the successive types
template IsType(T, Types...) {
    static if (Types.length)
        enum bool IsType = is(T == Types[0]) || IsType!(T, Types[1..$]);
    else
        enum bool IsType = true;
}

// true if T is string, wstring, or dstring
template IsString(T) {
    enum bool IsString = IsType!(T, string, wstring, dstring);
}

T input(T)(string msg) {
    write(msg);
    auto read = readln();
    static if (IsString!T)
        return to!T(read.chomp());
    else
        return to!T(read.strip());
}

// usage demo --------------
import std.stdio: writeln;
void main() {
    //auto x = input!string("Enter value x: ");
    auto x = input!double("Enter value x: ");
    writeln(">", x, "<");
}

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--- Comment #2 from bearophile_hugs@eml.cc 2011-02-08 13:13:01 PST ---
Adam Ruppe has suggested:

> I'd say make it do a combination of writef though, so you can do more complex prompts.
>
> auto number = ask!int("Enter a number, %s", name);

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--- Comment #3 from bearophile_hugs@eml.cc 2011-10-28 18:22:54 PDT ---
A D2 program that reads a string from the keyboard:


import std.stdio;
void main() {
    string s = readln();
    writeln(">", s, "<");
}


Running it it shows that the newline is left inside the string s:

...>test
123
>123
<


I don't know other languages where the command line input function leaves the
newline at the end of the input string. This is why in input() I have used
chomp().

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