Tcl - Down counter

Author

Down counter

Niv

2007-06-27, 7:12 pm

I want to display a down counter in days,hours, minutes (& maybe
seconds).
It's fairly easy to calculate the 3 or 4 parameters I require:

e.g.

set end [clock scan "September 1, 2007"]
set start [clock scan now]
set diff [expr $end -$start]
set secs [expr $diff - 60*($diff/60)]
set mins [expr ($diff - (($days*86400)+($hours*3600)))/60]
set hours [expr ($diff - ($days*86400))/3600]
set days [expr ($diff/86400)]

but how do I recalculate every so often (half second or 10 second
intervals) and then update the display.

I tried to loop the above with an "after 500" statement, but
everything locked up.

Can I use a trace command on, say, the secs variable?

Helmut Giese

2007-06-27, 7:12 pm

On Wed, 27 Jun 2007 06:06:11 -0700, Niv <kev.parsons@mbda.co.uk>
wrote:

>but how do I recalculate every so often (half second or 10 second
>intervals) and then update the display.
Hi Niv,
put the code which updates your display into a proc and use the nice
'every' idiom from http://wiki.tcl.tk/9299.
HTH
Helmut Giese

Niv

2007-06-27, 7:12 pm

On 27 Jun, 14:06, Niv <kev.pars...@mbda.co.uk> wrote:
> I want to display a down counter in days,hours, minutes (& maybe
> seconds).
> It's fairly easy to calculate the 3 or 4 parameters I require:
>
> e.g.
>
> set end [clock scan "September 1, 2007"]
> set start [clock scan now]
> set diff [expr $end -$start]
> set secs [expr $diff - 60*($diff/60)]
> set mins [expr ($diff - (($days*86400)+($hours*3600)))/60]
> set hours [expr ($diff - ($days*86400))/3600]
> set days [expr ($diff/86400)]
>
> but how do I recalculate every so often (half second or 10 second
> intervals) and then update the display.
>
> I tried to loop the above with an "after 500" statement, but
> everything locked up.
>
> Can I use a trace command on, say, the secs variable?

I've pasted the set "..." in the wrong order from my code, so ignore
that error please.
KP.

Glenn Jackman

2007-06-27, 7:12 pm

At 2007-06-27 09:06AM, "Niv" wrote:
> I want to display a down counter in days,hours, minutes (& maybe
> seconds).
> It's fairly easy to calculate the 3 or 4 parameters I require:
>
>
> e.g.
>
> set end [clock scan "September 1, 2007"]
> set start [clock scan now]
> set diff [expr $end -$start]
> set secs [expr $diff - 60*($diff/60)]
> set mins [expr ($diff - (($days*86400)+($hours*3600)))/60]
> set hours [expr ($diff - ($days*86400))/3600]
> set days [expr ($diff/86400)]
>
>
> but how do I recalculate every so often (half second or 10 second
> intervals) and then update the display.
>
> I tried to loop the above with an "after 500" statement, but
> everything locked up.
>
> Can I use a trace command on, say, the secs variable?

Have a look at http://wiki.tcl.tk/1011, particularly RS's
"every" proc for his digital clock in 3 lines of tcl.

Here's another way to calculate all the time params:

set ::end [clock scan "September 1, 2007"]
proc set_time_params {} {
global end days hours mins secs
set now [clock seconds]

set diff [expr {$end - $now}]
if {$diff < 0} {set diff 0}

set params [clock format $diff -format {%j %H %M %S} -gmt yes]

scan $params {%d %d %d %d} days hours mins secs
incr days -1

# next line for debugging
puts "${days}d ${hours}H ${mins}M ${secs}S"
}

# then, using RS's every:
proc every {ms body} {
eval $body
after $ms [list every $ms $body]
}
every 1000 set_time_params

Note, for testing I like to be able to cancel the every "infinite loop":

proc every {ms body} {
eval $body
set ::every_afterid [after $ms [list every $ms $body]]
}
proc cancel_every {} {
after cancel $::every_afterid
}

--
Glenn Jackman
"You can only be young once. But you can always be immature." -- Dave Barry

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