building fft

building fft

[otlore dolire]

I have a problem with a basic fft function i'm tryin to build. I think it's 
right, yet it raises conflicts, as if it didn't recognize the "end" at the 
end of it. Can you please tell me if someone sees something wrong? thx in 
advance

let rec fft N w y =
	let Y = make_vect N {Re = 0. ; Im = 0.}
	in
if N = 1 then begin Y.(0) <- y.(0) end
	 else
		begin	let m = div_int N 2;
			let l1 = make_vect m {Re = 0. ; Im = 0. }
		   	and l2 = make_vect m {Re = 0. ; Im = 0. }
			in for k = 0 to m - 1 do
		    	   l1.(k) <- y.(2*k);
		    	   l2.(k) <- y.(2*k + 1)
		   	done;
			   let L1 = make_vect m {Re = 0. ; Im = 0. }
		   	   and L2 = make_vect m {Re = 0. ; Im = 0. }
			  in
				for i = 0 to m - 1 do
				  L1.(i) <- (fft m (prod w w) l1).(i);
				  L2.(i) <- (fft m (prod w w) l2).(i)
				done;
		let wk = ref {Re = 1. ; Im = 0. }
		   and P = ref {Re = 0. ; Im = 0. }
		   and I = ref {Re = 0. ; Im = 0. }
		in for k=0 to m - 1 do
		    P := L1.(k);
		    I := prod !wk L2.(k);
		    Y.(k) <- prod (add !P !I) {Re = 0.5 ; Im = 0. };
		    Y.(k + m) <- prod (sous !P !I) {Re = 0.5 ; Im = 0. };
		    wk := prod !wk w
		  done
		end;
Y;;


PS: i defined the type cplx by type cplx = {Re : float ; Im : float}, prod, 
add and sous are respectively product, addition and substraction of cplx 
numbers

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Re: [Caml-list] building fft

[Jonathan Roewen]

variables have to start with a lowercase letter. values starting with
uppercase are module names/type constructors.

On 6/2/06, otlore dolire <otlore@hotmail.fr> wrote:
> I have a problem with a basic fft function i'm tryin to build. I think it's
> right, yet it raises conflicts, as if it didn't recognize the "end" at the
> end of it. Can you please tell me if someone sees something wrong? thx in
> advance
>
> let rec fft N w y =
>        let Y = make_vect N {Re = 0. ; Im = 0.}
>        in
> if N = 1 then begin Y.(0) <- y.(0) end
>         else
>                begin   let m = div_int N 2;
>                        let l1 = make_vect m {Re = 0. ; Im = 0. }
>                        and l2 = make_vect m {Re = 0. ; Im = 0. }
>                        in for k = 0 to m - 1 do
>                           l1.(k) <- y.(2*k);
>                           l2.(k) <- y.(2*k + 1)
>                        done;
>                           let L1 = make_vect m {Re = 0. ; Im = 0. }
>                           and L2 = make_vect m {Re = 0. ; Im = 0. }
>                          in
>                                for i = 0 to m - 1 do
>                                  L1.(i) <- (fft m (prod w w) l1).(i);
>                                  L2.(i) <- (fft m (prod w w) l2).(i)
>                                done;
>                let wk = ref {Re = 1. ; Im = 0. }
>                   and P = ref {Re = 0. ; Im = 0. }
>                   and I = ref {Re = 0. ; Im = 0. }
>                in for k=0 to m - 1 do
>                    P := L1.(k);
>                    I := prod !wk L2.(k);
>                    Y.(k) <- prod (add !P !I) {Re = 0.5 ; Im = 0. };
>                    Y.(k + m) <- prod (sous !P !I) {Re = 0.5 ; Im = 0. };
>                    wk := prod !wk w
>                  done
>                end;
> Y;;
>
>
> PS: i defined the type cplx by type cplx = {Re : float ; Im : float}, prod,
> add and sous are respectively product, addition and substraction of cplx
> numbers
>
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Re: [Caml-list] building fft

[Shawn]

otlore dolire wrote:
>
> PS: i defined the type cplx by type cplx = {Re : float ; Im : float}, 
> prod, add and sous are respectively product, addition and substraction 
> of cplx numbers
>

Besides the syntax errors from using capital-letter identifiers as field 
names, why are you reinventing the standard Complex module?