DEFAULT.html -- ACL2 Version 6.3

### DEFAULT

return the `:default` from the header of a 1- or 2-dimensional array

    Major Section:  ARRAYS

    Example Form:
    (default 'delta1 a)

    General Form:
    (default name alist)

where `name` is an arbitrary object and `alist` is a 1- or 2-dimensional array. This function returns the contents of the `:default` field of the header of `alist`. When `aref1` or `aref2` is used to obtain a value for an index (or index pair) not bound in `alist`, the default value is returned instead. Thus, the array `alist` may be thought of as having been initialized with the default value. `default` operates in virtually constant time if `alist` is the semantic value of `name`. See arrays.