9e216da9ef
After go1.16, go will use module mode by default, even when the repository is checked out under GOPATH or in a one-off directory. Add go.mod, go.sum to keep this repo buildable without opting out of the module mode. > go mod init github.com/mmcgrana/gobyexample > go mod tidy > go mod vendor In module mode, the 'vendor' directory is special and its contents will be actively maintained by the go command. pygments aren't the dependency the go will know about, so it will delete the contents from vendor directory. Move it to `third_party` directory now. And, vendor the blackfriday package. Note: the tutorial contents are not affected by the change in go1.16 because all the examples in this tutorial ask users to run the go command with the explicit list of files to be compiled (e.g. `go run hello-world.go` or `go build command-line-arguments.go`). When the source list is provided, the go command does not have to compute the build list and whether it's running in GOPATH mode or module mode becomes irrelevant.
134 lines
3.9 KiB
Plaintext
134 lines
3.9 KiB
Plaintext
// Koka language test module
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// This module implements the GarsiaWachs algorithm.
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// It is an adaptation of the algorithm in ML as described by JeanChristophe Filli<6C>tre:
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// in ''A functional implementation of the GarsiaWachs algorithm. (functional pearl). ML workshop 2008, pages 91--96''.
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// See: http://www.lri.fr/~filliatr/publis/gwWml08.pdf
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//
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// The algorithm is interesting since it uses mutable references shared between a list and tree but the
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// side effects are not observable from outside. Koka automatically infers that the final algorithm is pure.
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// Note: due to a current limitation in the divergence analysis, koka cannot yet infer that mutually recursive
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// definitions in "insert" and "extract" are terminating and the final algorithm still has a divergence effect.
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// However, koka does infer that no other effect (i.e. an exception due to a partial match) can occur.
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module garcsiaWachs
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import test = qualified std/flags
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# pre processor test
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public function main() {
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wlist = Cons1(('a',3), [('b',2),('c',1),('d',4),('e',5)])
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tree = wlist.garsiaWachs()
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tree.show.println()
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}
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//----------------------------------------------------
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// Trees
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//----------------------------------------------------
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public type tree<a> {
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con Leaf(value :a)
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con Node(left :tree<a>, right :tree<a>)
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}
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function show( t : tree<char> ) : string {
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match(t) {
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Leaf(c) -> core/show(c)
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Node(l,r) -> "Node(" + show(l) + "," + show(r) + ")"
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}
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}
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//----------------------------------------------------
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// Non empty lists
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//----------------------------------------------------
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public type list1<a> {
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Cons1( head : a, tail : list<a> )
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}
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function map( xs, f ) {
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val Cons1(y,ys) = xs
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return Cons1(f(y), core/map(ys,f))
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}
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function zip( xs :list1<a>, ys :list1<b> ) : list1<(a,b)> {
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Cons1( (xs.head, ys.head), zip(xs.tail, ys.tail))
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}
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//----------------------------------------------------
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// Phase 1
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//----------------------------------------------------
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function insert( after : list<(tree<a>,int)>, t : (tree<a>,int), before : list<(tree<a>,int)> ) : div tree<a>
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{
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match(before) {
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Nil -> extract( [], Cons1(t,after) )
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Cons(x,xs) -> {
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if (x.snd < t.snd) then return insert( Cons(x,after), t, xs )
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match(xs) {
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Nil -> extract( [], Cons1(x,Cons(t,after)) )
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Cons(y,ys) -> extract( ys, Cons1(y,Cons(x,Cons(t,after))) )
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}
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}
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}
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}
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function extract( before : list<(tree<a>,int)>, after : list1<(tree<a>,int)> ) : div tree<a>
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{
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val Cons1((t1,w1) as x, xs ) = after
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match(xs) {
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Nil -> t1
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Cons((t2,w2) as y, ys) -> match(ys) {
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Nil -> insert( [], (Node(t1,t2), w1+w2), before )
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Cons((_,w3),_zs) ->
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if (w1 <= w3)
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then insert(ys, (Node(t1,t2), w1+w2), before)
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else extract(Cons(x,before), Cons1(y,ys))
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}
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}
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}
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function balance( xs : list1<(tree<a>,int)> ) : div tree<a> {
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extract( [], xs )
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}
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//----------------------------------------------------
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// Phase 2
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//----------------------------------------------------
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function mark( depth :int, t :tree<(a,ref<h,int>)> ) : <write<h>> () {
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match(t) {
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Leaf((_,d)) -> d := depth
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Node(l,r) -> { mark(depth+1,l); mark(depth+1,r) }
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}
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}
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function build( depth :int, xs :list1<(a,ref<h,int>)> ) : <read<h>,div> (tree<a>,list<(a,ref<h,int>)>)
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{
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if (!(xs.head.snd) == depth) return (Leaf(xs.head.fst), xs.tail)
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l = build(depth+1, xs)
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match(l.snd) {
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Nil -> (l.fst, Nil)
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Cons(y,ys) -> {
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r = build(depth+1, Cons1(y,ys))
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(Node(l.fst,r.fst), r.snd)
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}
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}
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}
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//----------------------------------------------------
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// Main
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//----------------------------------------------------
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public function garsiaWachs( xs : list1<(a,int)> ) : div tree<a>
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{
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refs = xs.map(fst).map( fun(x) { (x, ref(0)) } )
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wleafs = zip( refs.map(Leaf), xs.map(snd) )
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tree = balance(wleafs)
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mark(0,tree)
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build(0,refs).fst
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}
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