RIGAL/rigdm218/ANALYSE.RIG

-- parsing of Prof. Blikle small language
--
-- file ANALYSE.RIG
--
#analyse_program
     (. (* $rez !.:= #analyse_stmt  * ';' )  [ ';' ]  .)
     / RETURN $rez /  ##

#analyse_stmt
    $rez := ( #assignment  !  #while_op  ) / RETURN $rez/ ;;

    (* $R !.:= S'( $$ <> ';' ) *)
    / report << unrecognised statement $R ; FAIL /
##

#assignment
    $var := #variable  ':=' $E := #expression  V'( $$ = ';' OR $$ = 'od')
    / RETURN 'assignment_op' :: <. left_part: $var,
                                   right_part: $E   .> /  ##

#while_op
    'while'  $E := #expression  'do'
             (* $body !.:= #analyse_stmt * ';' )
                                'od'
     / RETURN 'while_op' :: <. condition: $E,
                               body:   $body  .> /   ##

#expression
     $a1 := #arithm_expr
     [  '<'  $a2 := #arithm_expr
          / RETURN '<' :: <. arg1: $a1,  arg2: $a2 .>/ ]
     / RETURN $a1 /   ##

#arithm_expr
    $a1 := #term   / RETURN $a1 / ;;

    '('  $a1 := #arithm_expr  '+' $a2 := #arithm_expr  ')'
       / RETURN '+' :: <. arg1: $a1, arg2: $a2 .> /  ##

#term
    $NUM  / RETURN  $NUM /  ;;
    $rez :=   #variable    /RETURN $rez /  ##

#variable
    $R := ( w ! v ! x ! y ! z ) / RETURN $R /  ##