Exceptions.

%%% Raising (throwing) an exception 
declare
fun {Divide N M}
   if M \= 0
   then N div M
   else raise divByZero end
   end
end

{Browse {Divide 5 2}}
%{Browse {Divide 5 0}}
%%% Catching an exception:
try
   {Browse {Divide 5 0}}
catch divByZero then
   {Browse 'Division by zero is bad'}
end

%%% An exception can have a parameter
declare
fun {YearsUntilGraduation GradYear}
   if (GradYear < 2016 orelse GradYear > 2021)
   then raise invalidGradYear(GradYear) end
   else GradYear - 2016 end
end

{Browse {YearsUntilGraduation 2019}}

%%% The parameter can be used when the exception is caught
try
   {Browse {YearsUntilGraduation 2040}}
catch invalidGradYear(Year) then 
   {Browse 'The year '#Year#' is invalid'}
end
  

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