#include <flow.h>
#include <flow-term.h>

#define  SPACE(_T_,_N_)   REPLICATE( " ", {_T_}DIV-INTO(_N_) )

DEF-MAIN(argv,argc)
   CLR-SCR
   GOSUB( Print Grey Scale )
END

RUTINES

DEF-FUN( Print Grey Scale )
  SET( nrcolors, 8 )
  SET( direction, 1 )
  MSET( quarter, color )
  LOCATE( 0, 0 )
  FOR( LT?( quarter, 4 ), ++quarter )
      SET( height, 0 )
      FOR( LT?( height, 5 ), ++height )
          SET( width, 0 )
          FOR( LT?( width, nrcolors ), ++width )
              LET( color := CEIL( MUL( width, DIV( 255, SUB(nrcolors,1) ) ) ) )
              WHEN( NOT( MOD( direction, 2 ) ) ){
                  LET( color := SUB( 255, color ) )
              }
               PRN( COLOR-RGBB( color, color, color) SPACE( 128, nrcolors ) )
          NEXT
          PRNL("\OFF")
      NEXT
      nrcolors*=2
      ++direction
  NEXT
RET