三个 guard 都可使用 <code>z</code>。用 <code>let</code> 无法达到以上的效果。<ref>https://stackoverflow.com/q/4362328/10974106</ref><ref>[https://www.cse.iitb.ac.in/~as/fpcourse/haskell98_tutorial/patterns.html A Gentle Introduction to Haskell] 4.5 Lexical Scoping and Nested Forms</ref> | 三个 guard 都可使用 <code>z</code>。用 <code>let</code> 无法达到以上的效果。<ref>https://stackoverflow.com/q/4362328/10974106</ref><ref>[https://www.cse.iitb.ac.in/~as/fpcourse/haskell98_tutorial/patterns.html A Gentle Introduction to Haskell] 4.5 Lexical Scoping and Nested Forms</ref> |