From 074ad834c10410f54297f726a668d4403f92f8ec Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Fri, 9 Jul 2010 09:28:27 +0200
Subject: Implemented pattern matching

---
 src/Term.vala | 121 ++++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 105 insertions(+), 16 deletions(-)

(limited to 'src')

diff --git a/src/Term.vala b/src/Term.vala
index 46c03b3..5c27e7f 100644
--- a/src/Term.vala
+++ b/src/Term.vala
@@ -1,7 +1,20 @@
 namespace Eva {
   public interface Term : Object {
     public abstract string to_string();
-    public abstract bool equals(Term o);
+    
+    public bool equals(Term o) {
+      return (match(o) != null);
+    }
+    
+    public Gee.Map<string, Term>? match(Term o) {
+      Gee.Map<string, Term> vars = new Gee.HashMap<string, Term>();
+      if(!do_match(o, vars))
+        return null;
+      else
+        return vars;
+    }
+    
+    protected abstract bool do_match(Term o, Gee.Map<string, Term> vars);
     
     public abstract void encode(Erl.Buffer buffer);
     
@@ -109,7 +122,11 @@ namespace Eva {
       return value.to_string();
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(o is Int) {
         return value == (o as Int).value;
       }
@@ -137,7 +154,11 @@ namespace Eva {
       return value.to_string();
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(o is Int) {
         return value == (o as Int).value;
       }
@@ -166,7 +187,11 @@ namespace Eva {
       return value.to_string();
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(o is Double) {
         return value == (o as Double).value;
       }
@@ -213,7 +238,11 @@ namespace Eva {
       }
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(o is Atom) {
         return value == (o as Atom).value;
       }
@@ -254,7 +283,11 @@ namespace Eva {
       return ret + "}";
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(!(o is Tuple))
         return false;
       
@@ -264,7 +297,7 @@ namespace Eva {
         return false;
       
       for(int i = 0; i < value.size; ++i) {
-        if(!value[i].equals(t.value[i]))
+        if(!value[i].do_match(t.value[i], vars))
           return false;
       }
       
@@ -307,7 +340,11 @@ namespace Eva {
       tail = null;
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(o is List) {
         List l = o as List;
         
@@ -315,13 +352,13 @@ namespace Eva {
           return false;
         if((tail == null) != (l.tail == null))
           return false;
-        if(tail != null && !tail.equals(l.tail))
+        if(tail != null && !tail.do_match(l.tail, vars))
           return false;
         
         Gee.Iterator<Term> lt = l.list.iterator();
         lt.first();
         foreach(Term t in list) {
-          if(!t.equals(lt.get()))
+          if(!t.do_match(lt.get(), vars))
             return false;
           
           lt.next();
@@ -416,12 +453,16 @@ namespace Eva {
       return "\"" + value.replace("\\", "\\\\").replace("\"", "\\\"") + "\"";
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(o is String) {
         return (value == (o as String).value);
       }
       else if(o is List) {
-        return o.equals(this);
+        return o.do_match(this, vars);
       }
       else {
         return false;
@@ -452,7 +493,11 @@ namespace Eva {
       return "#Bin";
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(o is Binary) {
         Binary b = o as Binary;
         
@@ -490,7 +535,11 @@ namespace Eva {
       return "<" + node + "." + num.to_string() + "." + serial.to_string() + ">";
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(!(o is Pid))
         return false;
       
@@ -532,7 +581,11 @@ namespace Eva {
       return "#Port";
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(!(o is Port))
         return false;
       
@@ -579,7 +632,11 @@ namespace Eva {
       return "#Ref";
     }
     
-    public bool equals(Term o) {
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return o.do_match(this, vars);
+      }
+      
       if(!(o is Ref))
         return false;
       
@@ -616,4 +673,36 @@ namespace Eva {
       buffer.encode_ref(reference);
     }
   }
+  
+  public class Var : Term, Object {
+    public string name {get; construct;}
+    
+    public Var(string name0) {
+      assert(name0.get_char() == '_' || name0.get_char().isupper());
+      
+      Object(name: name0);
+    }
+    
+    public string to_string() {
+      return name;
+    }
+    
+    protected bool do_match(Term o, Gee.Map<string, Term> vars) {
+      if(o is Var) {
+        return name == (o as Var).name;
+      }
+      
+      if(name in vars) {
+        return vars[name].do_match(o, vars);
+      }
+      else {
+        vars[name] = o;
+        return true;
+      }
+    }
+    
+    public void encode(Erl.Buffer buffer) {
+      assert_not_reached();
+    }
+  }
 }
-- 
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