\section{Utility functions}

These are utility functions for use in other modules or
for the user interacting with LISP.  They all seem to be
related to hash tables for the moment.

<<util>>=
<<Set the current package>>
<<Display a hash table>>
<<Make a copy of a hash table>>
<<Check if a given key exists in a hash table>>
@ 
<<Set the current package>>=
(in-package max)
@ 

<<Display a hash table>>=
; Show a hash table in HenZo's cheesy format
(defun show-ht (ht)
        (format t "~%")
        (format t "Hash Table~%")
        (format t "----------~%")
        (maphash 
                #'(lambda (addr val) (format t "~a : ~a~%" addr val)) ; this..
                ht ; ...onto each element in this
        )
        (format t "~%")
)
@ 
<<Make a copy of a hash table>>=
; Returns a copy of hash-table ht
(defun copy-hash (ht)
        (let ((newhash (make-hash-table :size (hash-table-size ht) :test (hash-table-test ht))))
                (maphash
                        #'(lambda (key val) 
                                (setf (gethash key newhash) val)
                          )
                        ht
                )
        
                newhash
        )
)
@ 
Use the second of two values returned from gethash,
which indicates whether the looked-up item exists in the hash.
<<Check if a given key exists in a hash table>>=
; Return T if an item is in a hash table, NIL otherwise
(defun hash-exists (item ht)
        (nth-value 1 (gethash item ht))
)