From b5bfb6f025ce9dbbbd8353c6a019a0a428f4ddc6 Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Sun, 7 Aug 2022 00:09:32 +0200
Subject: Implemented the } (aka end) funge command

---
 src/pointer.zig    | 11 +++++++++--
 src/stack.zig      | 24 ++++++++++++++++++++++++
 src/stackStack.zig | 43 ++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 75 insertions(+), 3 deletions(-)

diff --git a/src/pointer.zig b/src/pointer.zig
index 70c9a28..7dbf566 100644
--- a/src/pointer.zig
+++ b/src/pointer.zig
@@ -160,8 +160,15 @@ pub const Pointer = struct {
                 p.sox = p.x + p.dx;
                 p.soy = p.y + p.dy;
             },
-            // TODO
-            '}' => return error.NotImplemented,
+            '}' => {
+                const v = p.ss.end() catch null;
+                if (v) |so| {
+                    p.sox = so[0];
+                    p.soy = so[1];
+                } else {
+                    p.reverse();
+                }
+            },
             // TODO
             'u' => return error.NotImplemented,
             'g' => {
diff --git a/src/stack.zig b/src/stack.zig
index 1a70be1..e02cb20 100644
--- a/src/stack.zig
+++ b/src/stack.zig
@@ -123,6 +123,30 @@ pub const Stack = struct {
         const fullResult = [_]i64{1};
         try std.testing.expectEqualSlices(i64, full.data.items, fullResult[0..]);
     }
+    pub fn discard(self: *Stack, n: u64) void {
+        // Implements a discard mechanism intended for use with the '}'(aka end) stackstack command
+        if (self.data.items.len > n) {
+            self.data.items.len -= n;
+        } else {
+            self.data.items.len = 0;
+        }
+    }
+    test "discard" {
+        var empty = try Stack.init(std.testing.allocator);
+        defer empty.deinit();
+        empty.discard(1);
+        const emptyResult = [_]i64{};
+        try std.testing.expectEqualSlices(i64, empty.data.items, emptyResult[0..]);
+        try empty.push(2);
+        empty.discard(3);
+        try std.testing.expectEqualSlices(i64, empty.data.items, emptyResult[0..]);
+        try empty.push(4);
+        try empty.push(5);
+        try empty.push(6);
+        empty.discard(1);
+        const emptyResult2 = [_]i64{ 4, 5 };
+        try std.testing.expectEqualSlices(i64, empty.data.items, emptyResult2[0..]);
+    }
 };
 
 test "all" {
diff --git a/src/stackStack.zig b/src/stackStack.zig
index 11943a7..208d85a 100644
--- a/src/stackStack.zig
+++ b/src/stackStack.zig
@@ -25,7 +25,7 @@ pub const StackStack = struct {
     pub fn begin(self: *StackStack, v: [2]i64) !void {
         var soss = self.toss;
         try self.data.append(soss);
-        var n = soss.pop();
+        const n = soss.pop();
         self.toss = try stack.Stack.init(self.allocator);
         if (n > 0) {
             try self.toss.transfert(soss, @intCast(u64, n));
@@ -78,6 +78,47 @@ pub const StackStack = struct {
         try std.testing.expectEqualSlices(i64, empty.data.items[2].data.items, sossResult3[0..]);
         try std.testing.expectEqualSlices(i64, empty.data.items[3].data.items, sossResult4[0..]);
     }
+    pub fn end(self: *StackStack) !?[2]i64 {
+        // Implements the '}' command behaviour which pops a stack from the stack stack
+        // returns null if a reflect should happen, a storage offset vector otherwise
+        if (self.data.popOrNull()) |soss| {
+            const n = self.toss.pop();
+            const v = soss.popVector();
+            if (n > 0) {
+                try soss.transfert(self.toss, @intCast(u64, n));
+            } else {
+                soss.discard(@intCast(u64, -n));
+            }
+            self.toss.deinit();
+            self.toss = soss;
+            return v;
+        } else {
+            return null;
+        }
+    }
+    test "end" {
+        var empty = try StackStack.init(std.testing.allocator);
+        defer empty.deinit();
+        try empty.toss.push(1);
+        try std.testing.expectEqual(empty.end(), null);
+        const tossResult = [_]i64{1};
+        try std.testing.expectEqualSlices(i64, empty.toss.data.items, tossResult[0..]);
+        try empty.toss.push(2);
+        try empty.toss.push(3);
+        try empty.toss.push(4);
+        try empty.toss.push(2);
+        try empty.begin([2]i64{ 5, 6 });
+        try empty.toss.push(7);
+        try empty.toss.push(2);
+        try std.testing.expectEqual(empty.end(), [2]i64{ 5, 6 });
+        const tossResult2 = [_]i64{ 1, 2, 4, 7 };
+        try std.testing.expectEqualSlices(i64, empty.toss.data.items, tossResult2[0..]);
+        try empty.toss.push(1);
+        try empty.begin([2]i64{ 8, 9 });
+        try empty.toss.push(-2);
+        try std.testing.expectEqual(empty.end(), [2]i64{ 8, 9 });
+        try std.testing.expectEqualSlices(i64, empty.toss.data.items, tossResult[0..]);
+    }
     pub inline fn toss(self: *StackStack) *stack.Stack {
         return self.toss;
     }
-- 
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