/*
 * Copyright (c) 2020 Galois, Inc.
 * Distributed under the terms of the BSD3 license (see LICENSE file)
 */

module Array where

primitive type Array : * -> * -> *

primitive arrayConstant : {a, b} b -> (Array a b)
primitive arrayLookup : {a, b} (Array a b) -> a -> b
primitive arrayUpdate : {a, b} (Array a b) -> a -> b -> (Array a b)

/**
 * Copy elements from the source array to the destination array.
 *
 * 'arrayCopy dest_arr dest_idx src_arr src_idx len' copies the
 * elements from 'src_arr' at indices '[src_idx ..< (src_idx + len)]' into
 * 'dest_arr' at indices '[dest_idx ..< (dest_idx + len)]'.
 *
 * The result is undefined if either 'dest_idx + len' or 'src_idx + len'
 * wraps around.
 */
primitive arrayCopy : {n, a} (Array [n] a) -> [n] -> (Array [n] a) -> [n] -> [n] -> (Array [n] a)
/**
 * Set elements of the given array.
 *
 * 'arraySet' arr idx val len' sets the elements of 'arr' at indices
 * '[idx ..< (idx + len)]' to 'val'.
 *
 * The result is undefined if 'idx + len' wraps around.
 */
primitive arraySet : {n, a} (Array [n] a) -> [n] -> a -> [n] -> (Array [n] a)
/**
 * Check whether the lhs array and rhs array are equal at a range of
 * indices.
 *
 * 'arrayRangeEq sym lhs_arr lhs_idx rhs_arr rhs_idx len' checks whether
 * the elements of 'lhs_arr' at indices '[lhs_idx ..< (lhs_idx + len)]' and
 * the elements of 'rhs_arr' at indices '[rhs_idx ..< (rhs_idx + len)]' are
 * equal.
 *
 * The result is undefined if either 'lhs_idx + len' or 'rhs_idx + len'
 * wraps around.
 */
primitive arrayRangeEqual : {n, a} (Array [n] a) -> [n] -> (Array [n] a) -> [n] -> [n] -> Bool

arrayRangeLookup : {a, b, n} (Integral a, fin n, LiteralLessThan n a) => (Array a b) -> a -> [n]b
arrayRangeLookup arr idx = res
  where
    res @ i = arrayLookup arr (idx + i)

arrayRangeUpdate : {a, b, n} (Integral a, fin n, LiteralLessThan n a) => (Array a b) -> a -> [n]b -> (Array a b)
arrayRangeUpdate arr idx vals = arrs ! 0
  where
    arrs = [arr] # [ arrayUpdate acc (idx + i) val | acc <- arrs | i <- [0 ..< n] | val <- vals ]