[metapost] exitif usage

[luigi scarso]

On Wed, Feb 15, 2017 at 7:36 PM, Walt Burkhard <burkhard at cs.ucsd.edu> wrote:
> Hello,
>
> I am using exitif within my metapost program and find many surprising output
> statements.    It seems that when the exitif statement is nested within a
> for statement as well as two if statements, these output messages appear.
>
> Here is a very short program to demonstrate this behavior.
>
> beginfig (1) ;
> for a = 0 upto 10 :
>   %% if ( a > 3 ) :
>     if ( a < 6 ) :
>       x := a*a ;
>       exitif ( x > 20 )
>     fi ;
>   message ( decimal x ) ;
>   %% fi ;
> endfor ;
> endfig ;
>
> beginfig (2) ;
> for a = 0 upto 10 :
>   if ( a > 3 ) :
>     if ( a < 6 ) :
>       x := a*a ;
>       exitif ( x > 20 )
>     fi ;
>   message ( decimal x ) ;
>   fi ;
> endfor ;
> endfig ;
> end
>
> Here is the output along with the warning message ---
>
> 0
> 1
> 4
> 9
> 16 [1]
> 16 [2] )
> (end occurred when if on line 22 was incomplete)
> 2 output files written: test.1 .. test.2
>
> Is there a mechanism to turn off such warning messages?
hm no, I fear not, it's a check hardcoded in the final cleanup.

Why not this:
beginfig (2) ;
x:=0;
for a = 0 upto 10 :
  if ( a > 3 ) :
    if ( a < 6 ) :
      x := a*a ;
    fi ;
  message "1) x=" & ( decimal x ) ;
  fi ;
  if (x>20): message "Quit!" ; fi  %useless, just to write something
  exitif ( x > 20 );
endfor ;
message "2) x=" & ( decimal x ) ;
endfig ;
end


Hans Hanges cooked this one

def quit_fi_fi_fi =
    fi fi fi
    exitif true
enddef ;

for a = 0 upto 10 :
    message "a=" & (decimal a);
    if ( a > 3 ) :
        if ( a < 6 ) :
            x := a*a ;
            message "0) x= " & (decimal x) ;
            if x > 20 :
                message "Quit!" ;
                quit_fi_fi_fi ;
            fi ;
        fi ;
        message "1) x= " & (decimal x) ;
    fi ;
endfor ;
message "2) x=" & (decimal x) ;
end


-- 
luigi