`gcombine``proc``seed``gen``gen2``...`procedureA generator for mapping with state. It yields a sequence of sub-folds over

`proc`.The

`proc`argument is a procedure that takes as many arguments as the input generators plus one. It is called as`(proc v1 v2 … seed)`, where`v1`,`v2`, ... are the values yielded from the input generators, and`seed`is the current seed value. It must return two values, the yielding value and the next seed. The result generator is exhausted when any of the`genn`generators is exhausted, at which time all the others are in an undefined state.