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cshandley.co.uk

10 pointsBruceEel6 comments

I remember using Amiga E, from a cover disk of CU Amiga.

Do I remember correctly that Amiga E had a "but" operator, which executes one statement but returns the value of the other? Never understood its point.

I thought it was one of those things that put Amiga ahead of competitors (because other systems had C/D). Oh my teenager brain.

Edit: looks like I remember correctly!: https://cshandley.co.uk/JasonHulance/beginner_93.html

That's some real esolang brain damage. Did somebody see the (four!) needlessly confusing increment and decrement operators in C and think this hadn't gone far enough?

It's not quite COME FROM but it sure is close for a supposedly useful language.

It's only doing what the https://en.wikipedia.org/wiki/Comma_operator does in C

Why you'd use it? Probably for reducing statements to expressions, e.g.

   PROC lower_delta(a1,a2,b1,b2) IS (da:=a2-a1) BUT (db:=b2-b1) BUT (IF da<db THEN da ELSE db)

That's just "I wish this was an expression language". Yeah, good idea, why isn't it?

    type Num = i32; // Or whatever your preferred numeric type is
    fn lower_delta(a1: Num, a2: Num, b1: Num, b2: Num) -> Num {
      let da = a2 - a1;
      let db = b2 - b1;
      if da < db { da } else { db }
    }

A more useful example I found:

  REPEAT
      ...
  UNTIL CtrlC() OR (IF m:=GetMsg(wnd.userport) THEN ReplyMsg(m) BUT 1 ELSE 0)

Which means loop until Ctrl-C is pressed, or an IDCMP message comes to the window (which must be replied to allow the sender to reuse/free the message, but otherwise we don't care what's in the message, because we know it's either a keypress or a mouseclick, and both end the loop).

The comma operator, or "BUT", lets us capture the result of GetMsg(), go down a positive "we got a message so end the loop" path, but also fits in a ReplyMsg() so we don't have to deal with it anywhere else

Like I said though, you wanted an expression language, just have an expression language

    loop {
      // ...
      if ctrl_c() ||
         match get_msg(wnd.userport) { None => false,
                                     Some(m) => { _ = reply_msg(m);   true } } {
         break;
      }
    }

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