Pine tree in gforth

tree.fs

( Program which prints a pine tree )
: star  ( -- ) ." *" ;
: stars ( n -- ) 0 do star loop ;

: padd  ( n1 n2 -- ) - spaces ;

: row   ( n1 n2 -- n1 ) 2dup padd dup + 1- stars ;

: tree  ( n -- ) dup 1 do I row cr loop ;

( Run with
  gforth tree.fs -e "10 tree bye"
          *
         ***
        *****
       *******
      *********
     ***********
    *************
   ***************
  *****************
  )