Historical errata for Mastering Clojure Macros

Output at bottom of the page indicates:

expected: (= 1 (throw (Exception.)))

but should be

expected: (= 1 (do (throw (Exception.)) 1))

Section “What’s in This Book? Chapter 2,”: ‘of’ missing in These are some the …
(Very minor typo indeed.)

Replace
Luckily, we can get the best of both worlds by wrapping a macro as a thin wrapper around the function version:
with
Luckily, we can get the best of both worlds by using a macro as a thin wrapper around the function version:

data List = Nil | Cons Int List

Well, Elm uses “type” instead of “data” as the reserved word for building algebraic data types.

In the code listing for `when.clj` the symbol `test` is in bold. (Probably because there is a core function named `test`.) I think this (and other code listings) would be easier for new readers if the `test` symbol was not bold.

The penultimate paragraph has a phrase “either remember know by heart.” I suspect that what was intended is “either remember or know by heart.”

The `cond` macro in `basics.cond.clj`, which ought to be recursive, calls out to the `clojure.core` version.

Solution: Delete the `clojure.core/` from the final line, changing the final form from
`(cons ’clojure.core/cond (next (next clauses)))`
to
`(cons ’cond (next (next clauses)))`

The same applies to the two subsequent examples.

join-input-lines takes separator as a parameter, then ignores it and uses a literal “,”. I’m pretty sure the intention was for separator to appear as the third argument in the call to replace.

This is a bit of a nitpick, but a macro can actually emit a call to a private function in a different namespace by derefing the fully qualified var which holds the function. I.e.

(@#’macro-ns/helper-func 1 2 3)

A couple of things here:
1) our-is uses the test/try-expr macro, not the try-expr function defined immediately prior.
2) The first arity of our-is calls f. To be true to the example, the call to f should only occur in the try-expr function.

The research on Scheme quoted on that page was conducted by Culpepper and Felleisen, not Culpepper and Felleison.