Introduction to Computer Science

NAME

timer, stoptimer - Create a timer that executes a function

SYNOPSIS

timer( ms, fun )
stoptimer( n )

DESCRIPTION

timer() creates a timer that will fire ms milliseconds after it is created. When it fires, the function passed in as fun will execute. The function should not include parentheses or arguments. Only the name of the function should be passed in as a reference. timer() returns an integer identifier that can be used to cancel the timer.

stoptimer() cancels a previously created timer that has not yet fired. The argument n should be the value returned by a earlier call to timer().

RETURN VALUE

timer() returns a unique identifier to the newly created timer.

stoptimer() has no return value.

ERRORS

Using parentheses for the fun argument when calling timer() produces a variety of unexpected behaviors.

EXAMPLES

The following example from page 10 of the Tranquility Manual
https://www.cs.drexel.edu/~bls96/tranquility.pdf implements a simple stopwatch.

var tim, lab, labstr, sec

fun init() {
     labstr : alloc(10)
     secs : 0
     html("<center0)
     lab : makelabel("0")
     html("<br>0)
     button("Start", swstart)
     button("Stop", swstop)
     button("Reset", swreset)
}

fun swstart() {
     tim : timer(1000, timestep)
}

fun swstop() {
     stoptimer(.tim)
}

fun swreset() {
     secs : 0
     setlabel(.lab, "0")
}


fun timestep() {
     time : timer(1000, timestep)
     secs : .secs + 1
     i2s(.labstr, .secs)
     setlabel(.lab, .labstr)
}

AUTHORS

Charlie Stuart cstuart11@protonmail.com

REPORTING BUGS

First, check the Tranquility Programmer’s Manual
https://www.cs.drexel.edu/~bls96/tranquility.pdf
If the problem persists see Dr. Stuart or Charlie Stuart

Dr. Stuart: brian.l.stuart@drexel.edu
Charlie Stuart: cstuart11@protonmail.com