Ch6, Ex15

declare
proc {Break}
   raise breakException end
end
proc {Block P}
   try {P Break}
   catch X then
      if X==breakException then skip
      else raise X end end
   end
end

%usage

%no break in statements, so prints one, two
{Block proc{$ Break} {Browse one} {Browse two} end}

%prints one only as after it {Break} is called
{Block proc{$ Break} {Browse one} {Break} {Browse two} end}

%nested blocks, it prints one, two and four... notice that
%calling Break in inner block breaks it only
{Block proc{$ Break1}
          {Browse one}
          {Block proc{$ Break2}
                    {Browse two} {Break2} {Browse three} end}
          {Browse four} end}