Use of # a.k.a. read-macro

Question

Reading book \"Let Over Lambda\" by Doug Hoyte, I found the following description of #. sign, a.k.a. read-macro:

A basic read macro that come

Answer 1

The experience shown me that in a big system composed of many parts, the "'" vs. the "#'" idiom makes patching easier. The reason is that the function object associated with the symbol is looked for every time it is encountered and this in every environment. Once and as soon as you've loaded (interactively, of course) a new definition (most likely, a patch) it is used the next time it is encountered. The performance cost is really small, but the advantage of the flexibility is huge. An it is really nice to imagine your customer's face when trying again the application saying "Wow! it works now!" :-)