Implement lvalue substr

sorear · May 5, 2011 · 79a8315 · 79a8315
1 parent 1f5854c
commit 79a8315
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Showing 2 changed files with 57 additions and 3 deletions.
diff --git a/lib/Builtins.cs b/lib/Builtins.cs
@@ -34,6 +34,42 @@ public class Builtins {
         }
     }
 
+    class SubstrLValue: Variable {
+        Variable backing;
+        int from;
+        int length;
+
+        public SubstrLValue(Variable backing, int from, int length) {
+            this.backing = backing;
+            this.from = from;
+            this.length = length;
+            // XXX Should binding a substr lvalue count as binding the original?
+            this.whence = null;
+            this.rw = backing.rw;
+            this.type = Kernel.StrMO;
+        }
+
+        public override P6any Fetch() {
+            string str = backing.Fetch().mo.mro_raw_Str.Get(backing);
+            return Kernel.BoxRaw<string>(Builtins.LaxSubstring2(str, from, length), Kernel.StrMO);
+        }
+
+        public override void Store(P6any v) {
+            string str = backing.Fetch().mo.mro_raw_Str.Get(backing);
+            int left = (from < 0) ? 0 : (from > str.Length) ? str.Length : from;
+            int right = ((length > (str.Length - left)) ? (str.Length - left) :
+                (length < 0) ? 0 : length) + left;
+            string lfr = str.Substring(0, left);
+            string mfr = v.mo.mro_raw_Str.Get(Kernel.NewROScalar(v));
+            string rfr = str.Substring(right);
+            backing.Store(Kernel.BoxRaw<string>(lfr + mfr + rfr, Kernel.StrMO));
+        }
+
+        public override Variable GetVar() {
+            return Kernel.BoxAnyMO<Variable>(this, Kernel.ScalarMO);
+        }
+    }
+
     public static string LaxSubstring(string str, int from) {
         if (from <= 0)
             return str;
@@ -175,13 +211,11 @@ public class Builtins {
     }
 
     public static Variable Substr3(Variable v1, Variable v2, Variable v3) {
-        P6any o1 = NominalCheck("$string", Kernel.AnyMO, v1);
         P6any o2 = NominalCheck("$start", Kernel.AnyMO, v2);
         P6any o3 = NominalCheck("$chars", Kernel.AnyMO, v3);
-        string r1 = o1.mo.mro_raw_Str.Get(v1);
         int r2    = (int)o2.mo.mro_raw_Numeric.Get(v2);
         int r3    = (int)o3.mo.mro_raw_Numeric.Get(v3);
-        return Kernel.BoxAnyMO<string>(LaxSubstring2(r1, r2, r3), Kernel.StrMO);
+        return new SubstrLValue(v1, r2, r3);
     }
 
     public static Variable Plus(Variable v1, Variable v2) {

diff --git a/test2.pl b/test2.pl
@@ -35,6 +35,26 @@
     is $i, 3, "last in for works";
 }
 
+{
+    my ($str, $v1, $v2);
+    $str = "abcdef";
+    substr($str,1,2) = "xy";
+    is $str, "axydef", "lvalue substr is functional";
+    $str = "abcdef";
+    substr($str,1,2) = "jklmno";
+    is $str, "ajklmnodef", "lvalue substr can change string length";
+    $str = "abcdef";
+    $v1 := substr($str,1,2);
+    $str = "xyzw";
+    is $v1, "yz", "substr return values read lazily";
+    $str = "abcdef";
+    $v1 := substr($str,0,1);
+    $v2 := substr($str,3,1);
+    $v1 = "xx";
+    $v2 = "yy";
+    is $str, "xxbyydef", "substr thunks track by index";
+}
+
 #is $?FILE, 'test.pl', '$?FILE works';
 #is $?ORIG.substr(0,5), '# vim', '$?ORIG works';