Restarting a piece of code

Andrej Bauer

Alex Baretta
 Alex Baretta

Alex Baretta
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Date:   (:) 
From:  Alex Baretta <alex@b...> 
Subject:  Re: [Camllist] Restarting a piece of code 
Andrej Bauer wrote: > > Can we avoid having to pass treshold around directly? You can imagine > that users won't be too thrilled about this sort of thing. I think you can. See arithmetic functions as building blocks for computationsrather than computations themselveswhich are parametric with respect to the threshold value. let unit_expression _ = assert false let imaginary_unit_expression _ = assert false let addition_expression _ = assert false let negative_expression _ = assert false let multiplication_expression _ = assert false let inverse_expression _ = assert false let exponential_expression _ = assert false let logarithm_expression _ = assert false exception Overflow let rec compute grow_threshold threshold_transformation = fun computation threshold > try computation (compute grow_threshold) (threshold_transformation threshold) with Overflow > let new_threshold = grow_threshold threshold in computation (compute grow_threshold) (threshold_transformation new_threshold) (* Here we define the primitive operations of the algebraic structure *) (* We don't mind if the primitive operations are a little heavy, so *) (* long as it is easy to compose them to form complex computations. *) let one = fun compute threshold > unit_expression threshold let i = fun compute threshold > imaginary_unit_expression threshold let add x y = fun compute threshold > let x' = compute x threshold in let y' = compute y threshold in addition_expression x y threshold let neg x = fun compute threshold > let x' = compute x threshold in negative_expression x threshold let mul x y = fun compute threshold > let x' = compute x threshold in let y' = compute y threshold in multiplication_expression x y threshold let inv x = fun compute threshold > let x' = compute x threshold in inverse_expression x threshold let exp x = fun compute threshold > let x' = compute x threshold in exponential_expression x threshold let log x = fun compute threshold > let x' = compute x threshold in logarithm_expression x threshold (* Let's say these are all the basic computations we need. Now we can *) (* start building more computations on top of these. *) let sub x y = add x (neg y) let div x y = mul x (inv y) let pow x y = exp (mul (log x) y) let root x y = exp (mul (log x) (inv y)) let two = add one one let twoi = add i i let cos x = div (add (exp (mul i x)) (exp (neg (mul i x)))) two let sin x = div (sub (exp (mul i x)) (exp (neg (mul i x)))) twoi > I sense monads. Or am I looking for dynamic binding? You are looking for partial evaluation/multistage programming, but you don't necessarily have to delve into MetaOcaml to solve your problem. As you can see you can generate a homomorphism from the calculus of imaginary numbers to the calculus of computations of imaginary numbers which can be directly represented in Ocaml. > Best regards, > > Andrej >  ********************************************************************* http://www.barettadeit.com/ Baretta DE&IT A division of Baretta SRL tel. +39 02 370 111 55 fax. +39 02 370 111 54 Our technology: The Application System/Xcaml (AS/Xcaml) <http://www.asxcaml.org/> The FreerP Project <http://www.freerp.org/>