OpenEuphoria

Re: Need help with PD source (again)

• Posted by Matt Lewis <matthewwalkerlewis at gmail.com> Apr 04, 2005
• 422 views

Pete Lomax wrote:
> 
> >
> Matt Lewis wrote:
> > So it's those ENDFOR_INT_UP1's and ENDFOR_GENERAL's that you need to 
> > reproduce.
>
> You would need additional goto's after them, to properly exit the
> loop, should you be on the last iteration. I think you would be better
> off jumping to the existing endfor/endwhile statement instead.
> Branch straightening might tidy things up automatically, with luck.

That seems wasteful (execution-wise) and requires changing the back end,
anyway.  It was actually pretty simple to do.  I basically had to create
a couple of stacks to remember the loop type, variable and the backpatch
addresses, and added a continue statement.  In the for-loop case, I just
added an exit right after the ENDFOR statement (ENDWHILE just jumps back
to the while statement for evaluation).  Here's what the new routine looks 
like:

procedure Continue_statement()
	token tok
	integer bp1, bp2
	sequence s
	if preprocess then
	    CompileErr("continue not allowed in preprocessing")
	end if
		
	if not loop_stack[$] then
	    CompileErr( "continue must be inside of loop" )

	elsif loop_stack[$] = FOR then
	    StartSourceLine(TRUE)
	    op_info1 = loop_sym_stack[$]
	    op_info2 = loop_bp_stack[$] + 1
		s = Pop() & Pop()
		Push( s[2] )
		Push( s[1] )
	    emit_op(ENDFOR_GENERAL) -- will be set at runtime by FOR op
		Push( s[2] )
		Push( s[1] )
	    emit_op(EXIT)
	    AppendXList(length(Code)+1)
	    emit_forward_addr()     -- to be back-patched 
	    tok = next_token()
	    putback(tok)
	    
	elsif loop_stack[$] = WHILE then
		bp1 = loop_bp_stack[$][1]
		bp2 = loop_bp_stack[$][1]
	    StartSourceLine(TRUE)
	    emit_op(ENDWHILE)
	    emit_addr(bp1)
	    	
	end if

end procedure

 
> How about duplicating AppendXList/PatchXList in parser.e?

I don't know what you mean by this...

Matt Lewis