[Richard Suchenwirth] 2003-02-12 - The following little state machine was created, 
with help from [dkf], in the [Tcl chatroom], instigated by the quote (Alan Cox?): "A 
computer is a state machine. Threads are for people who can't program state machines."

So here is one, starting with the necessary state transition command - [goto in Tcl].
}
 proc goto label {
    upvar 1 nextstate nextstate
    set nextstate $label
    return -code continue
 }
if 0 {The "machine" itself takes a paired list of labels and state code; if a state code 
does not end in a ''goto'', the same state will be repeated as long as not left, with 
''goto'' or [break]. Execution starts at the first of the states.
}
 proc statemachine states {
    array set state $states
    set nextstate [lindex $states 0]
    while 1 {eval $state($nextstate)}
 }
# Testing: a tiny state machine that greets you as often as you wish:

 statemachine {
    1 {
	puts "how often?"
	gets stdin nmax
	if {$nmax==""} break
	set n 0
	goto 2
    }
    2 {
	if {[incr n] > $nmax} {goto 1}
	puts "hello"
    }
 }

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[Category Concept] | [Arts and crafts of Tcl-Tk programming]