Implementing forward refs in monadic assembler and interpreter

[Axel Simon]

On Fri, Nov 15, 2002 at 01:38:03AM -0800, Mike Gunter wrote:
> 
>   \begin{code}
>   compute12	= mdo 
>     { 		zero r1 
>     ;		zero r2
>     ; 		addi r2 3	-- loop three times
>     ;topLoop <-	label
>     ;		addi r1 4
>     ;		addi r2 (-1)	-- decrement loop counter
>     ;		brPositive r2 topLoop
>     ;		mov r3 r1
>     ;		addi r3 (-10)	
> -- !!! Forward branch:
>     ;		brPositive r3 out -- if r1 > 10 don't add 100
>     ;		add r1 100
>     ;out <-	label
>     }
>   \end{code}
> 
> but it's not clear to me how to implement it.

I would suggest a forward declaration like in Pascal. At least it would 
fit the monadic style:

     out <- forwardLabel
     brPositive r3 out
     add r1 100
     fLabelSet out

I admit it doesn't look that nice, but it's easy to implement.

Axel.