From 59d076f6dc179315b6dfc1c141dc9ee48cc66a54 Mon Sep 17 00:00:00 2001
From: mryouse
Date: Tue, 6 Jun 2023 20:27:18 -0400
Subject: initial commit of reverse

---
 chunk.d    | 20 ++++++++++++++++++++
 compiler.d | 15 +++++++++++++++
 vm.d       |  4 ++++
 3 files changed, 39 insertions(+)

diff --git a/chunk.d b/chunk.d
index 21ebb9d..fb1f97c 100644
--- a/chunk.d
+++ b/chunk.d
@@ -47,6 +47,7 @@ abstract class Seq {
     abstract Seq rest();
     abstract Seq most();
     abstract Value last();
+    abstract Seq reverse();
     abstract int length();
     abstract bool isIn(Value val);
 }
@@ -76,6 +77,15 @@ class String : Seq {
         return new String(this.str[0..$ - 1]);
     }
 
+    override Seq reverse() {
+        string s = "";
+        int end = to!int(this.str.length) - 1;
+        for (int i = end; i >= 0; i--) {
+            s ~= this.str[i];
+        }
+        return new String(s);
+    }
+
     override Value last() {
         return makeStringValue(to!string(this.str[$ - 1]));
     }
@@ -155,6 +165,15 @@ class List : Seq {
         return ret;
     }
 
+    override Seq reverse() {
+        int length = to!int(this.inner.length);
+        List ret = new List(length);
+        for (int i = 0; i < length; i++) {
+            ret.addItemAtIndex(this.inner[i], length - i - 1);
+        }
+        return ret;
+    }
+
     override Value last() {
         return this.inner[$ - 1];  // this fails on NIL
     }
@@ -225,6 +244,7 @@ enum OpCode {
     OP_MEMBER,
     OP_MOST,
     OP_REST,
+    OP_REVERSE,
 
     // DEFINITIONS/VARIABLES
     OP_CONSTANT,
diff --git a/compiler.d b/compiler.d
index 6756882..51fca25 100644
--- a/compiler.d
+++ b/compiler.d
@@ -662,6 +662,18 @@ class Compiler {
         this.func.chunk.writeOp(OpCode.OP_REST, args[0].line);
     }
 
+    void compileReverse(Form[] args) {
+        // TODO how do we identify/propagate errors?
+        if (args.length != 1) {
+            this.error("'reverse': expected [1] argument, received ?", -1);
+            return;
+        }
+        ValueType vt = this.resolve(args[0], ValueType.OBJ); // TODO need a new type
+        this.func.chunk.writeOp(OpCode.OP_TYPE_CHECK_SEQ, args[0].line);
+
+        this.func.chunk.writeOp(OpCode.OP_REVERSE, args[0].line);
+    }
+
     // TERMINAL
     void compilePrint(Form[] args) {
         if (args.length != 1) {
@@ -843,6 +855,9 @@ class Compiler {
             case "rest":
                 this.compileRest(cons.tail);
                 break;
+            case "reverse":
+                this.compileReverse(cons.tail);
+                break;
 
             // OTHER
             case "print":
diff --git a/vm.d b/vm.d
index a8d3d6e..db2d4a0 100644
--- a/vm.d
+++ b/vm.d
@@ -475,6 +475,10 @@ class VM {
                     Seq seq = asSeq(this.popA());
                     this.pushA(makeNumberValue(seq.length()));
                     break;
+                case OpCode.OP_REVERSE:
+                    Seq seq = asSeq(this.popA());
+                    this.pushA(makeSeqValue(seq.reverse()));
+                    break;
                 case OpCode.OP_MEMBER:
                     Seq seq = asSeq(this.popA());
                     Value val = this.popA();
-- 
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