[magicmouse]

In practice any JS programmer will find that the use of the undefined value is very familiar. In Beads it is abbreviated to U as it is used constantly, because the default value of something in the graph data structures is U.

For symmetry reasons, the error and undefined values work across all types, which cleans up one of the messes in JS, where you have undefined, NaN, null, and goodness knows what else. That we have a uniform error value for nodes is a very minor point; it is almost impossible to generate an error value in the protected arithmetic world of Beads. Square root of -1 is one of the only ways I can think of.

There is no try/except in Beads, there are no exceptions as all functions are total, and all arithmetic closed (like Excel).