When designing these primitives, I think there are a few considerations: When creating a new execution context, which one should begin executing, and which one

When designing these primitives, I think there are a few considerations: When creating a new execution context, which one should begin executing, and which one should be bound to a local variable in the executing one? Should there be any primitive that switches to an already-existing execution context without creating a copy of it? How many primitives should there be? call/cc answers: "The new execution context should begin executing and the old one should be bound to a local variable, no, one" As a person who occasionally explains these things to people who have never been exposed to them, I strongly prefer: "The old execution context should continue executing and the new one should be bound to a local variable, yes, as many as we need to produce the preceding answers" I think without trying too hard you can get the number of primitives in the latter case down to three, "create", "copy", and "switch." If you wanted to bug your users you could get it down to two.