Add OP_WITHIN page

Author: thunderbiscuit

.vitepress/config.js

@@ -178,7 +178,7 @@ export default {
         { text: "<code>162 | OP_GREATERTHANOREQUAL</code>", link: "/opcodes/OP_GREATERTHANOREQUAL.md" },
         { text: "<code>163 | OP_MIN</code>", link: "/opcodes/OP_MIN.md" },
         { text: "<code>164 | OP_MAX</code>", link: "/opcodes/OP_MAX.md" },
-        { text: "<code>165 | 🚧 OP_WITHIN</code>", link: "/opcodes/OP_WITHIN.md" },
+        { text: "<code>165 | OP_WITHIN</code>", link: "/opcodes/OP_WITHIN.md" },
         { text: "<code>166 | OP_RIPEMD160</code>", link: "/opcodes/OP_RIPEMD160.md" },
         { text: "<code>167 | OP_SHA1</code>", link: "/opcodes/OP_SHA1.md" },
         { text: "<code>168 | OP_SHA256</code>", link: "/opcodes/OP_SHA256.md" },

opcodes/OP_MIN.md

@@ -9,14 +9,15 @@
 `OP_MIN` compares the top two items on the stack as integers and pushes the smaller value back onto the stack. Both original items are removed, and the smaller value becomes the new top item.
 
 ### Operation
+
 1. Pop the top item and the second item from the stack.
 2. Compare the two items, and push the smaller of the two values onto the stack.
 
 ### Notes
 
 - Both items must be valid integers. Bitcoin Script interprets byte arrays up to **4 bytes** as integers.
 - An empty array (`[]`) is treated as 0 when compared.
-- If there are fewer than two items on the stack when `OP_GREATERTHAN` is executed, the script will fail.
+- If there are fewer than two items on the stack when `OP_MIN` is executed, the script will fail.
 
 ## Examples
 

opcodes/OP_WITHIN.md

@@ -1,5 +1,64 @@
-# Work In Progress
+# OP_WITHIN
 
-:::warning
-This page has not yet been written. If you have experience with bitcoin Script and would like to contribute, please do! You can open a PR [on the repository for this website](https://github.com/thunderbiscuit/opcode-explained).
+:::info
+**Opcode number:** 165  
+**Byte representation:** `0xa5`  
+**Short description:** Pop the top three items; if the first item is within the range specified by the second and third stack items, push 1, otherwise, push an empty array.  
 :::
+
+`OP_WITHIN` checks if the top item on the stack is within a specified range. Specifically, it evaluates whether the first item is greater than or equal to the second item and less than the third item (min <= x < max). If true, it pushes 1 (true) onto the stack; otherwise, it pushes an empty array (false).
+
+### Operation
+
+1. Pop the top three items from the stack:
+    - x (fist item): The value to check.
+    - min (second item): The lower bound of the range.
+    - max (third item): The upper bound of the range.
+2. Evaluate whether min <= x < max:
+    - If true, push 1 (true) onto the stack.
+    - If false, push an empty array (false) onto the stack.
+
+### Notes
+
+- The range is _inclusive_ of the lower bound (min <= x) and _exclusive_ of the upper bound (x < max).
+- Both items must be valid integers. Bitcoin Script interprets byte arrays up to **4 bytes** as integers.
+- An empty array (`[]`) is treated as 0 when compared.
+- If there are fewer than two items on the stack when `OP_GREATERTHAN` is executed, the script will fail.
+
+## Examples
+
+### Example 1: Value is within the range
+
+```shell
+# ASM script
+OP_2 OP_1 OP_3 OP_WITHIN
+
+# Raw script
+525153a5
+
+# Stack (before OP_WITHIN)
+3  # max
+1  # min
+2  # x
+
+# Stack (after OP_WITHIN)
+1  # true, as 1 <= 2 < 3
+```
+
+### Example 3: Value is at the lower bound
+
+```shell
+# ASM script
+OP_1 OP_1 OP_3 OP_WITHIN
+
+# Raw script
+515153a5
+
+# Stack (before OP_WITHIN)
+3  # top (max)
+1  # min
+1  # x
+
+# Stack (after OP_WITHIN)
+1  # true, as 1 <= 1 < 3
+```