[racket] Printing multiple stmts in cond

From: Richard Cleis (rcleis at mac.com)
Date: Sat Apr 30 03:28:27 EDT 2011

(if (condition? data)
    (FF x1 x2 xNEW x3 x4)
    (f x1 x2 x3 x4))

The result of one of them is returned.


On Apr 30, 2011, at 1:16 AM, nikhil wrote:

> Ok. Here's what I am trying to do.
> I am parsing incoming racket code and generating back racket code. 
> In my case, I have an incoming function which takes 4 arguments and I need to generate a function which takes in 5 args when a condition satisfies, if not then the original 4 args .
> Something like,
> Input--> 
> (f x1 x2 x3 x4)
> Output-->
> (FF x1 x2 xNEW x3 x4)
> --------------------------------------------------
> (define (parse-func exp)
>    (cond
> ............
>    [(f? exp)
>        `(FF
>          ,x1
>          ,x2
>          ,(if (condition?)
>               xNEW)
>          ,x3
>          ,x4)]
> (The above is just pseudo-code) As shown above, when the if condition fails I just want 4 args. But a default #<void> is passed instead when used with cond. 
> I am new to racket and functional programing in general, so I am not able to express my problem very accurately :(
> Hope the above example is clear enough to explain what I am doing. 
> On Sat, Apr 30, 2011 at 7:00 AM, Neil Van Dyke <neil at neilvandyke.org> wrote:
> nikhil wrote at 04/30/2011 02:52 AM:
> Basically, I dont want to execute an else stmt or return multiple values. I just want to return "stmt1" if condition satisfies and dont do anything if false. No returning #<void> or anything.
> An expression always produces at least one value, even if the value is the void value.  (Usually, a REPL will hide a returned void value from you, but a void value is still being returned, which can be confusing.)
> If you can show *why* you don't want to produce *any* value, then people can show you different ways to write that code.
> -- 
> http://www.neilvandyke.org/
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