Hi,

let me start from my bus example again.

Suppose we want to increase cost in a loop, we used to be able to write

tuple bus
{
 key int sizeBus;
 float costBus;
}

{bus} buses={<40,500>,<30,400>};

// Now suppose we need to increase cost 20%

execute
{
for(var b in buses) b.costBus=1.2*b.costBus;

writeln(buses);
}

But for many years now this gives an error about b being used already. And that's safe.

What we can write instead:

tuple bus
{
 key int sizeBus;
 float costBus;
}

{bus} buses={<40,500>,<30,400>};

// Now suppose we need to increase cost 20%
range rangeBuses=0..card(buses)-1;

execute
{
for(var indexbus in rangeBuses)
{
    var b=Opl.item(buses,indexbus);
    b.costBus=1.2*b.costBus;
}
writeln(buses);
}

which works and gives

{<40 600> <30 480>}

Not as easy to write as before but that leads to less bugs. (Less bugs but as many buses)

regards