Mastering Clojure Macros

Approaching Hygiene with the Gensym

In order to avoid symbol capture issues like the one we just saw, Clojure gives us a few tools, all related to the gensym function. gensym’s job is simple: it produces a symbol with a unique name. The names will look funny because the name needs to be unique for the application, but that’s OK because we never need to type them into code:

As you can see, any given invocation of gensym gives a unique value back—so if you want to refer to the same one twice, you’ll need to hold onto the value with a let binding or something similar. ...