yieldm was located in ::tcl::unsupported in beta releases of Changes in Tcl/Tk 8.6. Later, yieldto was modified such that it became trivial to implement yieldm in terms of it. Thereafter, ::tcl::unsupported::yieldm was removed.
yieldm is like yield, except that the next time the the associated coroutine context command is executed, it behaves like a procedure whose argument specification is the single special value, args. I.e. the coroutine context accepts an arbitrary number of arguments, and the return value of yieldm is a list of those arguments. yieldm is no-longer a built-in command, but can be implemented like this:
proc yieldm {{value {}}} {
yieldto return -level 0 $value
}In this implementation, any command that simply returns $value could be used instead of return:
proc yieldm {{value {}}} {
yieldto lindex $value
}DKF: I'd rather use string cat for this:
proc yieldm {{value ""}} {
yieldto string cat $value
}AMG: Is any progress being made towards officially adopting this command or a variation thereof?
MS did not see any: no TIP, no requests