bundles/org.simantics.scl.runtime/src/org/simantics/scl/runtime/unification/Unification.java

   1 package org.simantics.scl.runtime.unification;
   2
   3 import org.simantics.scl.runtime.function.Function;
   4 import org.simantics.scl.runtime.tuple.Tuple;
   5 import org.simantics.scl.runtime.tuple.Tuple0;
   6
   7
   8 public class Unification {
   9     public static Object canonical(Object a) {
  10         if(a instanceof UVar) {
  11             UVar ua = (UVar)a;
  12             if(ua.bound)
  13                 return ua.ref = canonical(ua.ref);
  14             else
  15                 return a;
  16         }
  17         return a;
  18     }
  19
  20     @SuppressWarnings("unchecked")
  21     public static void unify(Object a, Object b) {
  22         a = canonical(a);
  23         b = canonical(b);
  24         if(a == b)
  25             return;
  26         if(a instanceof UVar) {
  27             ((UVar)a).setRef(b);
  28             return;
  29         }
  30         if(b instanceof UVar) {
  31             ((UVar)b).setRef(a);
  32             return;
  33         }
  34         if(a instanceof UPending) {
  35             ((UPending)a).checkAgains(b);
  36             return;
  37         }
  38         if(b instanceof UPending) {
  39             ((UPending)b).checkAgains(a);
  40             return;
  41         }
  42         if(a instanceof UCons) {
  43             UCons ua = (UCons)a;
  44             if(b instanceof UCons) {
  45                 UCons ub = (UCons)b;
  46                 if(ua.tag.id != ub.tag.id)
  47                     throw new RuntimeUnificationException();
  48                 unifyTuple(ua.components, ub.components);
  49                 ua.components = ub.components;
  50             }
  51             else {
  52                 Object bComponents = ua.tag.destructor.apply(b);
  53                 unifyTuple(ua.components, bComponents);
  54                 ua.components = bComponents;
  55             }
  56         }
  57         else {
  58             if(b instanceof UCons) {
  59                 UCons ub = (UCons)b;
  60                 Object aComponents = ub.tag.destructor.apply(a);
  61                 unifyTuple(aComponents, ub.components);
  62                 ub.components = aComponents;
  63             }
  64             else {
  65                 if(a == null ? b != null : !a.equals(b))
  66                     throw new RuntimeUnificationException();
  67             }
  68         }
  69     }
  70
  71     public static void unifyTuple(Object a, Object b) {
  72         if(a instanceof Tuple) {
  73             Tuple ta = (Tuple)a;
  74             Tuple tb = (Tuple)b;
  75             int length = ta.length();
  76             for(int i=0;i<length;++i)
  77                 unify(ta.get(i), tb.get(i));
  78         }
  79         else {
  80             unify(a, b);
  81         }
  82     }
  83
  84     @SuppressWarnings({ "rawtypes", "unchecked" })
  85     public static Object extractWithDefault(Function def, Object uni) {
  86         if(uni instanceof UVar) {
  87             UVar var = (UVar)uni;
  88             if(var.bound)
  89                 return var.ref = extractWithDefault(def, var.ref);
  90             else {
  91                 var.bound = true;
  92                 return var.ref = def.apply(Tuple0.INSTANCE);
  93             }
  94         }
  95         else if(uni instanceof UCons) {
  96             UCons cons = (UCons)uni;
  97             return cons.tag.constructor.apply(cons.components);
  98         }
  99         else if(uni instanceof UPending) {
 100             UPending pending = (UPending)uni;
 101             return pending.force();
 102         }
 103         else
 104             return uni;
 105     }
 106 }