The function
mailbox-peek
returns the first object in the mailbox without removing it. If the mailbox is empty,
nil
is returned.
If the mailbox
mailbox
is not empty, the function
mailbox-peek
returns the first object in the mailbox without removing it. The second returned value
value-p
is
t
.
If
mailbox
is empty, both return values
result
and
value-p
are
nil
.
mailbox-peek
needs to lock the mailbox, which means it is significantly slower than mailbox-not-empty-p, and also may affect other processes. In most of the cases, mailbox-not-empty-p is sufficient and hence is preferable.LispWorks User Guide and Reference Manual - 21 Dec 2011