From 362fdc1118ebe4699df05a4cbb0bbbe8f2a30a59 Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Mon, 8 Aug 2022 21:41:55 +0200
Subject: Implemented the under funge command

---
 src/pointer.zig    |  7 +++++--
 src/stackStack.zig | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/src/pointer.zig b/src/pointer.zig
index 7dbf566..7578a65 100644
--- a/src/pointer.zig
+++ b/src/pointer.zig
@@ -169,8 +169,11 @@ pub const Pointer = struct {
                     p.reverse();
                 }
             },
-            // TODO
-            'u' => return error.NotImplemented,
+            'u' => {
+                if (p.ss.under() catch true) {
+                    p.reverse();
+                }
+            },
             'g' => {
                 const v = p.ss.toss.popVector();
                 try p.ss.toss.push(p.field.get(v[0] + p.sox, v[1] + p.soy));
diff --git a/src/stackStack.zig b/src/stackStack.zig
index 208d85a..a76d304 100644
--- a/src/stackStack.zig
+++ b/src/stackStack.zig
@@ -119,6 +119,55 @@ pub const StackStack = struct {
         try std.testing.expectEqual(empty.end(), [2]i64{ 8, 9 });
         try std.testing.expectEqualSlices(i64, empty.toss.data.items, tossResult[0..]);
     }
+    pub fn under(self: *StackStack) !bool {
+        if (self.data.items.len == 0) {
+            return true;
+        }
+        const n = self.toss.pop();
+        var soss = self.data.items[self.data.items.len - 1];
+        if (n > 0) {
+            var i: usize = 0;
+            while (i < n) : (i += 1) {
+                try self.toss.push(soss.pop());
+            }
+        } else {
+            var i: usize = 0;
+            while (i < -n) : (i += 1) {
+                try soss.push(self.toss.pop());
+            }
+        }
+        return false;
+    }
+    test "under" {
+        var empty = try StackStack.init(std.testing.allocator);
+        defer empty.deinit();
+        try empty.toss.push(1);
+        try std.testing.expectEqual(empty.under(), true);
+        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(5);
+        try empty.toss.push(6);
+        try empty.toss.push(0);
+        try empty.begin([2]i64{ 7, 8 });
+        try empty.toss.push(9);
+        try empty.toss.push(0);
+        try std.testing.expectEqual(empty.under(), false);
+        const tossResult2 = [_]i64{9};
+        try std.testing.expectEqualSlices(i64, empty.toss.data.items, tossResult2[0..]);
+        try empty.toss.push(2);
+        try std.testing.expectEqual(empty.under(), false);
+        const tossResult3 = [_]i64{ 9, 8, 7 };
+        try std.testing.expectEqualSlices(i64, empty.toss.data.items, tossResult3[0..]);
+        try empty.toss.push(-1);
+        try std.testing.expectEqual(empty.under(), false);
+        const tossResult4 = [_]i64{ 9, 8 };
+        const sossResult = [_]i64{ 1, 2, 3, 4, 5, 6, 7 };
+        try std.testing.expectEqualSlices(i64, empty.toss.data.items, tossResult4[0..]);
+        try std.testing.expectEqualSlices(i64, empty.data.items[0].data.items, sossResult[0..]);
+    }
     pub inline fn toss(self: *StackStack) *stack.Stack {
         return self.toss;
     }
-- 
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