link complete
August 14, 1996; Richard L. Goerwitz
This file is in the public domain.
complete(s,st) completes a s relative to a set or list of strings, st.
Put differently, complete() lets you supply a
partial string, s, and get back those strings in st
that s is either equal to or a substring of.
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Lots of command interfaces allow completion of partial input.
Complete() simply represents my personal sentiments about how this
might best be done in Icon. If you strip away the profuse comments
below, you end up with only about thirty lines of actual source
code.
I have arranged things so that only that portion of an automaton
which is needed to complete a given string is actually created and
stored. Storing automata for later use naturally makes complete()
eat up more memory. The performance gains can make it worth the
trouble, though. If, for some reason, there comes a time when it
is advisable to reclaim the space occupied by complete's static
structures, you can just call it without arguments. This
"resets" complete() and forces an immediate garbage collection.
Example code:
commands := ["run","stop","quit","save","load","continue"]
while line := read(&input) do {
cmds := list()
every put(cmds, complete(line, commands))
case *cmds of {
0 : input_error(line)
1 : do_command(cmds[1])
default : display_possible_completions(cmds)
}
etc...
More Iconish methods might include displaying successive
alternatives each time the user presses the tab key (this would,
however, require using the nonportable getch() routine). Another
method might be to use the first string suspended by complete().
NOTE: This entire shebang could be replaced with a slightly slower
and much smaller program suggested to me by Jerry Nowlin and Bob
Alexander.
procedure terscompl(s, st)
suspend match(s, p := !st) & p
end
This program will work fine for lists with just a few members, and
also for cases where s is fairly large. It will also use much less
memory.