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+# $EPIC: prefix.txt,v 1.4 2006/08/19 04:05:34 sthalik Exp $
+======Synopsis:======
+$__prefix__(<word list>)
+======Technical:======
+   * If the <word list> argument is omitted the empty string is returned.
+   * The return value of this function is whatever string is the common initial substring (CIS) of all of the words in <word list>.  If there is no CIS in <word list>, the empty string is returned.
+   * This function uses an O(M*N) algorithm where M is the number of words in <word list> and N is the length of the first word in <word list>. Take this into consideration when planning.
+======Practical:======
+This function can be used to do pseudo-completion.  To explain,
+consider if you are working on a tab completion script and the user
+types "foo" and presses tab.  Normally you would extract from $[[onchannel]]()
+everything that matched "foo*", but what if that returns more than one
+word?  It is considerate to the user to complete as much as possible for
+them and then prompt them for the rest.  So let's say that you had two
+users, "foobar" and "foobaz".  When the user pressed <tab> after typing
+"foo" you would do something like this:
+<file>
+# Some code goes here to put "foo" in $input.
+@ users = filter($input* $onchannel())
+@ result = prefix($users)
+if (numwords($users) > 1) { beep }
+# Some code goes here to remove the 'foo' from the input
+#   line and paste $result in its place.
+</file>
+$result will contain "fooba" because "fooba" is the CIS of the word
+list (foobar foobaz).  So when the user presses <tab> you will put the
+string "fooba" in place of "foo" and beep to let them know that it is
+not an exact match.  You could use $users to tell them what their options
+are, if you wanted to.
+If the user typed something like "boo" and there were no users on the
+channel whose nickname started with "boo", then $result would be the
+empty string.  You could trap that as well and give the user an error
+message.
+======Returns:======
+The Common Initial Substring (CIS) of all of the words in <word list>
+======Examples:======
+<file>
+$prefix(foobar foobaz foobooya)      returns "foob"
+$prefix(one two three)               returns the empty string.
+</file>