package bigarray-compat

To each element kind is associated an OCaml type, which is the type of OCaml values that can be stored in the big array or read back from it. This type is not necessarily the same as the type of the array elements proper: for instance, a big array whose elements are of kind float32_elt contains 32-bit single precision floats, but reading or writing one of its elements from OCaml uses the OCaml type float, which is 64-bit double precision floats.

The GADT type ('a, 'b) kind captures this association of an OCaml type 'a for values read or written in the big array, and of an element kind 'b which represents the actual contents of the big array. Its constructors list all possible associations of OCaml types with element kinds, and are re-exported below for backward-compatibility reasons.

Using a generalized algebraic datatype (GADT) here allows to write well-typed polymorphic functions whose return type depend on the argument type, such as:

let zero : type a b. (a, b) kind -> a = function
  | Float32 -> 0.0 | Complex32 -> Complex.zero
  | Float64 -> 0.0 | Complex64 -> Complex.zero
  | Int8_signed -> 0 | Int8_unsigned -> 0
  | Int16_signed -> 0 | Int16_unsigned -> 0
  | Int32 -> 0l | Int64 -> 0L
  | Int -> 0 | Nativeint -> 0n
  | Char -> '\000'

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

See Bigarray.char.

As shown by the types of the values above, big arrays of kind float32_elt and float64_elt are accessed using the OCaml type float. Big arrays of complex kinds complex32_elt, complex64_elt are accessed with the OCaml type Complex.t. Big arrays of integer kinds are accessed using the smallest OCaml integer type large enough to represent the array elements: int for 8- and 16-bit integer bigarrays, as well as OCaml-integer bigarrays; int32 for 32-bit integer bigarrays; int64 for 64-bit integer bigarrays; and nativeint for platform-native integer bigarrays. Finally, big arrays of kind int8_unsigned_elt can also be accessed as arrays of characters instead of arrays of small integers, by using the kind value char instead of int8_unsigned.

kind_size_in_bytes k is the number of bytes used to store an element of type k.

• since 4.03.0

See Bigarray.fortran_layout.

To facilitate interoperability with existing C and Fortran code, this library supports two different memory layouts for big arrays, one compatible with the C conventions, the other compatible with the Fortran conventions.

In the C-style layout, array indices start at 0, and multi-dimensional arrays are laid out in row-major format. That is, for a two-dimensional array, all elements of row 0 are contiguous in memory, followed by all elements of row 1, etc. In other terms, the array elements at (x,y) and (x, y+1) are adjacent in memory.

In the Fortran-style layout, array indices start at 1, and multi-dimensional arrays are laid out in column-major format. That is, for a two-dimensional array, all elements of column 0 are contiguous in memory, followed by all elements of column 1, etc. In other terms, the array elements at (x,y) and (x+1, y) are adjacent in memory.

Each layout style is identified at the type level by the phantom types Bigarray.c_layout and Bigarray.fortran_layout respectively.

Zero-dimensional arrays. The Array0 structure provides operations similar to those of Bigarray.Genarray, but specialized to the case of zero-dimensional arrays that only contain a single scalar value. Statically knowing the number of dimensions of the array allows faster operations, and more precise static type-checking.

One-dimensional arrays. The Array1 structure provides operations similar to those of Bigarray.Genarray, but specialized to the case of one-dimensional arrays. (The Array2 and Array3 structures below provide operations specialized for two- and three-dimensional arrays.) Statically knowing the number of dimensions of the array allows faster operations, and more precise static type-checking.

Two-dimensional arrays. The Array2 structure provides operations similar to those of Bigarray.Genarray, but specialized to the case of two-dimensional arrays.

Three-dimensional arrays. The Array3 structure provides operations similar to those of Bigarray.Genarray, but specialized to the case of three-dimensional arrays.

Return the generic big array corresponding to the given zero-dimensional big array.

• since 4.05.0

Return the generic big array corresponding to the given one-dimensional big array.

Return the generic big array corresponding to the given two-dimensional big array.

Return the generic big array corresponding to the given three-dimensional big array.

Return the zero-dimensional big array corresponding to the given generic big array. Raise Invalid_argument if the generic big array does not have exactly zero dimension.

• since 4.05.0

Return the one-dimensional big array corresponding to the given generic big array. Raise Invalid_argument if the generic big array does not have exactly one dimension.

Return the two-dimensional big array corresponding to the given generic big array. Raise Invalid_argument if the generic big array does not have exactly two dimensions.

Return the three-dimensional big array corresponding to the given generic big array. Raise Invalid_argument if the generic big array does not have exactly three dimensions.

reshape b [|d1;...;dN|] converts the big array b to a N-dimensional array of dimensions d1...dN. The returned array and the original array b share their data and have the same layout. For instance, assuming that b is a one-dimensional array of dimension 12, reshape b [|3;4|] returns a two-dimensional array b' of dimensions 3 and 4. If b has C layout, the element (x,y) of b' corresponds to the element x * 3 + y of b. If b has Fortran layout, the element (x,y) of b' corresponds to the element x + (y - 1) * 4 of b. The returned big array must have exactly the same number of elements as the original big array b. That is, the product of the dimensions of b must be equal to i1 * ... * iN. Otherwise, Invalid_argument is raised.

Specialized version of Bigarray.reshape for reshaping to zero-dimensional arrays.

• since 4.05.0

Specialized version of Bigarray.reshape for reshaping to one-dimensional arrays.

Specialized version of Bigarray.reshape for reshaping to two-dimensional arrays.

Specialized version of Bigarray.reshape for reshaping to three-dimensional arrays.