tputs $channel yes\n
    } else {
      tputs $channel no\n
    }
  }
 
  proc checkForTiming { channel threshold {tries 2} } {

    tputs $channel "---- checking for precision timing... "

    #
    # HACK: Sometimes the first try takes quite a bit longer than subsequent
    #       tries.  We attempt to bypass this problem by retrying a set number
    #       of times (which can be overridden by the caller) before giving up.
    #

    set difference unknown

    for {set try 0} {$try < $tries} {incr try} {
      #
      # NOTE: Attempt to block for exactly one second.
      #
      set start [expr {[clock clicks -milliseconds] & 0x7fffffff}]
      after 1000; # wait for "exactly" one second.
      set stop [expr {[clock clicks -milliseconds] & 0x7fffffff}]

................................................................................
      #
      # NOTE: Are we within the threshold specified by the caller?
      #
      if {$difference >= 0 && $difference <= $threshold} then {
        #
        # NOTE: We appear to be capable of fairly precise timing.
        #



        addConstraint timing


        tputs $channel [appendArgs "yes (0 <= " $difference " <= " \
            $threshold " milliseconds, tried " [expr {$try + 1}] \
            " " [expr {$try > 0 ? "times" : "time"}] ")\n"]

        #
        # NOTE: We are done here, return now.
        #
        return
      }
    }

    tputs $channel [appendArgs "no (0 <= " $difference " > " \
        $threshold " milliseconds)\n"]

  }
 
  proc checkForPerformance { channel } {
    tputs $channel "---- checking for performance testing... "

    #
    # NOTE: Are we allowed to do performance testing?

      tputs $channel yes\n
    } else {
      tputs $channel no\n
    }
  }
 
  proc checkForTiming { channel threshold {constraint ""} {tries 1} } {
    tputs $channel [appendArgs \
        "---- checking for precision timing (" $threshold " milliseconds)... "]

    #
    # HACK: Sometimes the first try takes quite a bit longer than subsequent
    #       tries.  We attempt to bypass this problem by retrying a set number
    #       of times (which can be overridden by the caller) before giving up.
    #
    set try 0
    set difference unknown

    for {} {$try < $tries} {incr try} {
      #
      # NOTE: Attempt to block for exactly one second.
      #
      set start [expr {[clock clicks -milliseconds] & 0x7fffffff}]
      after 1000; # wait for "exactly" one second.
      set stop [expr {[clock clicks -milliseconds] & 0x7fffffff}]

................................................................................
      #
      # NOTE: Are we within the threshold specified by the caller?
      #
      if {$difference >= 0 && $difference <= $threshold} then {
        #
        # NOTE: We appear to be capable of fairly precise timing.
        #
        if {[string length $constraint] > 0} then {
          addConstraint $constraint
        } else {
          addConstraint timing
        }

        tputs $channel [appendArgs "yes (0 <= " $difference " <= " \
            $threshold " milliseconds, tried " [expr {$try + 1}] \
            " " [expr {$try + 1 > 1 ? "times" : "time"}] ")\n"]

        #
        # NOTE: We are done here, return now.
        #
        return
      }
    }

    tputs $channel [appendArgs "no (0 <= " $difference " > " \
        $threshold " milliseconds, tried " $try " " \
        [expr {$try > 1 ? "times" : "time"}] ")\n"]
  }
 
  proc checkForPerformance { channel } {
    tputs $channel "---- checking for performance testing... "

    #
    # NOTE: Are we allowed to do performance testing?

  # NOTE: Has performance testing been disabled?
  #
  if {![info exists no(performance)]} then {
    checkForPerformance $test_channel
  }

  #







  # NOTE: Have precision timing tests been disabled?
  #
  if {![info exists no(timing)]} then {
    checkForTiming $test_channel 50; # 1/20th second.
  }

  #
  # NOTE: Has interactive testing been disabled?

  # NOTE: Has performance testing been disabled?
  #
  if {![info exists no(performance)]} then {
    checkForPerformance $test_channel
  }

  #
  # NOTE: Have very precise timing tests been disabled?
  #
  if {![info exists no(preciseTiming)]} then {
    checkForTiming $test_channel 25 preciseTiming; # 1/40th second.
  }

  #
  # NOTE: Have precise timing tests been disabled?
  #
  if {![info exists no(timing)]} then {
    checkForTiming $test_channel 50; # 1/20th second.
  }

  #
  # NOTE: Has interactive testing been disabled?