The
:element-type
argument in open and
with-open-file
defaults to the value of
*default-character-element-type*.
If
element-type
is not
:default
, checks are made to ensure that the resulting stream's stream-element-type is compatible with its external format:
:input
or
:io
, the
element-type
argument must be a supertype of the type of characters produced by the external format.
:output
or
:io
, the
element-type
argument must be a subtype of the type of characters accepted by the external formatIf the element-type argument doesn't satisfy these requirements, an error is signalled.
If
element-type
is
:default
the system chooses the stream-element-type on the basis of the external format.