Handling integer overflow in TCL

[itzmesri]

Hi,
I am facing integer overflow issues in TCL. All I want to do is to calculate an alarm timer(in milli seconds) upon elapsing which some functionality has to be kick started.

But the calculation (since it is in milliseconds) results in a negative value.

Is there are a way to over come this issue ?

 

[prex1]

It depends on how many days you want to be represented in the timeout. An integer in Tcl is a C long, so it should hold at least 20 days expressed in milliseconds, before going to the negative side.

Franco

http://www.xcalcs.com

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[itzmesri]

Yes, the aim is to have the number of days configurable. I am looking into a range of around 50 to 100 days. Is there an alternative way to handle this problem ?

 

[prex1]

Don't see an immediate solution, as the field to after (if you are using it) is an integer.
What you could do is writing an after command that, for the first n executions, will execute after again, and only at n+1 will execute the actual command.
n and the delay (less than 20 days) would be calculated to sum up to the total delay.

Franco

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[itzmesri]

Thanks.
Yes I am in deed using the after command
I am not able to quite get your previous suggestion. I presume you mean to say that we use the after command in increments and calculate the total delay ?

 

[prex1]

Well something like

set n [expr round($timeout_in_days/20)]
set timeout_ms [expr int($timeout_in_days/$n*86400000)]
after $timeout_ms repeat_one $n $timeout_ms
proc repeat_one {n t} {
  incr n -1
  if {$n} {
    after $t repeat_one $n $t
  } else {
    do_whatever
  }
}

Franco

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[itzmesri]

Thanks a lot!
Works now.