Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.javascript > #30601

Re: An "if" without "if"

Show all headers | View raw

Stefan Ram wrote:

>   Could I use arrow functions to emulate an »if«?
>
>   Here is one observation (only user input to the
>   console is shown):
>
> a = undefined;
> ( ( x = console.log( "ok" )) => 0 )( a );
> a = 1;
> ( ( x = console.log( "ok" )) => 0 )( a );
>
>   So I have written a function that will print »ok«
>   /if and only if/ »a« is undefined.

That doesn't really rely a lot on arrow functions, but rather on the 
distinction of arguments to use default values or not. And there are 
many of such control flow branchings in the language. The simplest way 
to emulate an if-statement would probably be

   while (/* condition */) {
       /* conditional statements */
       break;
   }

But since you are interested in functions, I'd recommend to use 
something along the lines of

   const when = t => f => c => ({true:f, false:f}[!!c]);

Now you can do

   const log = when(()=>console.log("ok"))(()=>console.log("not ok");
   log(1)() // ok
   log(0)() // not ok
   log(true)() // ok
   log(false)() // not ok
   log(…)() // and so on

You also might be interested in Church Booleans.

Kind regards,
  Bergi

Back to comp.lang.javascript | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: An "if" without "if" andber93@web.de - 2016-06-02 02:16 +0200
  Re: An "if" without "if" Stefan Weiss <krewecherl@gmail.com> - 2016-06-02 12:37 +0200
    Re: An "if" without "if" Scott Sauyet <scott@sauyet.com> - 2016-07-03 00:13 +0000
      Re: An "if" without "if" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-07-03 11:07 +0100
      Re: An "if" without "if" "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-07-03 10:29 -0700
        Re: An "if" without "if" Scott Sauyet <scott@sauyet.com> - 2016-07-04 01:08 +0000
      Re: An "if" without "if" John Harris <niam@jghnorth.org.uk.invalid> - 2016-07-04 14:49 +0100

csiph-web