CTMCP Section 2.9 Exercise 12

CTMCP-Section2.9-12.oz

declare FinallyExample Eval

fun {Eval E}
   if {IsNumber E} then E
   else
      case E
      of plus(X Y) then {Eval X} + {Eval Y}
      [] times(X Y) then {Eval X} * {Eval Y}
      else raise illFormedExpr(E) end
      end
   end
end

fun {FinallyExample E}
   local R V in
      try
	 try
	    V={Eval E}
	    R=false
	    raise V end
	 catch X then
	    R=true
	    raise X end
	 end
      catch Y then
	 {Browse '*** Finally Block ***'}
	 if R then raise Y end
	 else V
	 end
      end      
   end
end

try
   {Browse {FinallyExample plus(plus(5 5) 10)}}
   {Browse {FinallyExample times(6 11)}}
   {Browse {FinallyExample minus(7 10)}}
catch illFormedExpr(E) then
   {Browse '*** Ilegal expression '#E#' ***'}
end