From 3ac15b135664f659347c8b4598c2ca37718716ed Mon Sep 17 00:00:00 2001
From: "jtriley.eth" <Jtriley15@gmail.com>
Date: Tue, 16 Apr 2024 11:19:17 -0700
Subject: [PATCH] add behavior

---
 README.md | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/README.md b/README.md
index 6e6faf3..6bb16d5 100644
--- a/README.md
+++ b/README.md
@@ -60,6 +60,21 @@ contract Vault {
 }
 ```
 
+### Behavior
+
+- Each external call asserts:
+  - The call succeeded.
+  - The call returned the correct returndatasize.
+  - If the call returns a boolean:
+    - The call returned `true`.
+  - If the call is ERC20's `transfer`, `transferFrom`, or `approve`:
+    - No data was returned OR (the returndata is 32 bytes AND is `true`).
+- The operators `+`, `-`, `*`, `/`, and `%` revert if the operation:
+  - Overflows.
+  - Underflows.
+  - Divides by zero.
+- The operator `~` masks the address to `160` bits after performing bitwise `not`.
+
 ### Existing Types
 
 Documentation is prefixed to respective type and function definitions.