lists as sequences, first and rest

1 files changed, 27 insertions, 3 deletions

diff --git a/chunk.d b/chunk.d
index 0573687..70d7b1c 100644
--- a/chunk.d
+++ b/chunk.d
@@ -8,7 +8,6 @@ import dbg;
 enum ObjType {
     FUNCTION,
     SCRIPT,
-    LIST,
 }
 
 abstract class Obj {
@@ -37,18 +36,41 @@ class Function : Obj {
     }
 }
 
-class List : Obj {
+enum SeqType {
+    LIST,
+    STRING,
+}
+
+abstract class Seq {
+    SeqType type;
+    abstract Value first();
+    abstract Seq rest();
+}
+
+class List : Seq {
     Value[] inner;
 
     this(int length) {
         this.inner = new Value[length];
-        this.type = ObjType.LIST;
+        this.type = SeqType.LIST;
     }
 
     void addItemAtIndex(Value item, int idx) {
         this.inner[idx] = item;
     }
 
+    override Value first() {
+        return this.inner[0];  // this fails on NIL
+    }
+
+    override Seq rest() {
+        List ret = new List(to!int(this.inner.length) - 1);
+        for (int i = 1; i < this.inner.length; i++) {
+            ret.addItemAtIndex(this.inner[i], i - 1);
+        }
+        return ret;
+    }
+
     override string toString() {
         return format("list ('%s' + %d)", printableValue(this.inner[0]), this.inner.length - 1);
     }
@@ -85,11 +107,13 @@ enum OpCode {
     OP_CONCAT,  // No?
 
     OP_FIRST,   // No?
+    OP_REST,
 
     OP_TYPE_CHECK_NUMBER,
     OP_TYPE_CHECK_BOOLEAN,
     OP_TYPE_CHECK_STRING,
     OP_TYPE_CHECK_LIST,
+    OP_TYPE_CHECK_SEQ,
 }
 
 class Chunk {