]> On Thursday 25 December 2003 21:41, Grégory Guyomarc'h wrote: > Hello, > > Does anyone know how to index bigarrays with negative integers as in > fortran (either through a modified version of Bigarray or some > pre-Processing macro with caml-p4)? For those who wonder, it is for a pde > numerical code, i wish i could index boundary cells naturally as u.{-1} > u.{-2}, ... and u.{n+1}, u.{n+2}, ... Or if you have any experience in > implementing such numerical code in OCaml and want to suggest better > options, i am also interested :o). One way is to make a record type like this type ifunc = { lo: int; (* lowest index inside the boundaries *) hi: int; (* highest index inside the boundaries *) f: int -> float; } and then wrap your bigarray like this: #load "bigarray.cma";; open Bigarray let b = Array1.create float64 c_layout 32;; let ifunc_of_ba ba = let n = Array1.dim ba in let rec f = fun i -> if i < 0 then f(n+i) else if i >= n then f(i-n) else ba.{i} in { lo = 0; hi = n-1; f = f; } # let b2 = ifunc_of_ba b;; val b2 : ifunc = {lo = 0; hi = 31; f = <fun>} (* now let's look at the uninitialized values in the bigarray **) # b2.f(-1);; - : float = 8.75916002045846257e+189 # b2.f(-2);; - : float = 1.96098134143591667e+243 # b2.f(32+1);; - : float = 5.66882172258997e-228 # b2.f(32+2);; - : float = -1.24992649718407699e+65 # b2.f(1);; - : float = 5.66882172258997e-228 # b2.f(2);; - : float = -1.24992649718407699e+65 It wasn't really clear from your message how you wanted to handle the boundary conditions, so I made them periodic. I hope this helps. -- Issac Trotts ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners