the apt package to install changed names years ago, and I didn't notice

README.md

@@ -30,7 +30,7 @@ solution that appears incorrect.
 
 You will need the following external tools installed:
 - Haskell and Stack
-  - On Ubuntu, this is `sudo apt-get install haskell-platform`
+  - On Ubuntu, this is `sudo apt-get install haskell-stack`
   - On a Mac, do this with `brew install haskell-stack`
 - Dealer, a domain-specific language to generate bridge hands
   - On Ubuntu, run `sudo apt-get install dealer`