18 lines
383 B
Forth
18 lines
383 B
Forth
integer function fib(n)
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integer, intent(in) :: n
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if (n < 0 ) then
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write (*,*) 'Bad argument: fib(',n,')'
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stop
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else
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fib = purefib(n)
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end if
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contains
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recursive pure integer function purefib(n) result(f)
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integer, intent(in) :: n
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if (n < 2 ) then
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f = n
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else
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f = purefib(n-1) + purefib(n-2)
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end if
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end function purefib
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end function fib
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