Proposal of a general do-while loop [more generic and tested

[Taro Kawagishi]

downs Wrote:

> Here's a more generic version. This one was tested and shown to work.
> Have fun with it!
>   --downs
> =======================================================================
> import std.stdio, std.string;
> 
> /// Cond is
> void doWhile(P, C, O)(lazy P pre, lazy C cond, lazy O post) {
>    while (true) {
>      static if (is(P==void delegate())) pre()(); else pre();
>      if (!cond()) break;
>      static if (is(O==void delegate())) post()(); else post();
>    }
> }
> 
> // these are the things stupid std.string forces us to do.
> // Tango, with str.length==NOTFOUND, really picked the better approach.
> int find(char[] str, char[] match, int offset) {
>    auto res=std.string.find(str[offset..$], match);
>    if (res==-1) return -1;
>    return res+offset;
> }
> 
> void main() {
>    int pos=0;
>    auto text="This interestingly works.";
>    // Note the way we can switch between using brackets and not using them.
>    doWhile(
>      pos=text.find("i", pos),
>      pos+1, /// equivalent to pos!=-1, except it also demonstrates
>             /// that the conditional can be anything "if" can use.
>      { writefln("Hit at ", pos); ++pos; }
>    );
> }

I am new to D, and this is quite impressive.
I guess we can do a similar thing with function objects in C++.
However my original intention was to do simple things in a simple way.

-Taro