On 3/17/2012 15:03, Antti J Ylikoski wrote:
In his legendary book series The Art of Computer Programming,
Professor Donald E. Knuth presents many of his algorithms in the form
that they have been divided in several individual phases, with
instructions to GOTO to another phase interspersed in the text of the
individual phases.
I. e. they look like the following, purely invented, example: (Knuth is
being clearer than me below.....)
A1. (Do the work of Phase A1.) If <zap> then go to Phase A5,
otherwise continue.
A2. (Do some work.) If <zorp> go to Phase A4.
A3. (Some more work.)
A4. (Do something.) If <condition ZZZ> go to Phase A1.
A5. (Something more). If <foobar> then go to Phase A2, otherwise
end.
I came across the problem, which would be the clearest way to program
such algorithms with a programming language such as Python, which has
no GOTO statement. It struck me that the above construction actually
is a modified Deterministic Finite Automaton with states A1 -- A5 +
[END], transferring to different states, not on read input, but
according to conditions in the running program.
A1 and A5 are NOT states: they're labels.
There is no garanteed bijection from labels to states.
So one very clear way to program Knuth with Python is the following
kind of a construct.
[...]
Your way is easy, but the result is poor.
Your should try to rewrite it. Decompilers do exactly that.
Kiuhnm
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