prog8/examples/fibonacci.p8

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2019-01-27 00:02:45 +00:00
%import c64utils
; This example computes the first 20 values of the Fibonacci sequence.
; It uses the feature that variables that don't have an initialization value,
; will retain their previous value over multiple invocations of the program or subroutine.
; This is extremely handy for the Fibonacci sequence because it is defined
; in terms of 'the next value is the sum of the previous two values'
~ main {
sub start() {
c64scr.print("fibonacci sequence\n")
fib_setup()
for ubyte i in 0 to 20 {
c64scr.print_uw(fib_next())
c64.CHROUT('\n')
}
}
sub fib_setup() {
; (re)start the sequence
main.fib_next.prev=0
main.fib_next.current=1
}
sub fib_next() -> uword {
uword prev ; no init value so will retain previous value
uword current ; no init value so will retain previous value
uword new = current + prev
prev = current
current = new
return prev
}
}