Open arrays

Often fixed size arrays turn out to be too inflexible; procedures should be able to deal with arrays of different sizes. The openarray type allows this; it can only be used for parameters. Open arrays are always indexed with an int starting at position 0. The len, low and high operations are available for open arrays too. Any array with a compatible base type can be passed to an open array parameter, the index type does not matter. In addition to arrays, sequences can also be passed to an open array parameter.

The openarray type cannot be nested: multidimensional open arrays are not supported because this is seldom needed and cannot be done efficiently.

proc testOpenArray(x: openArray[int]) = echo repr(x)
testOpenArray([1,2,3])  # array[]
testOpenArray(@[1,2,3]) # seq[]