Macros

Like Clojure, Calcit uses macros to support new syntax. And macros ared evaluated during building to expand syntax tree. A defmacro block returns list and symbols, as well as literals:

defmacro noted (x0 & xs)
  if (empty? xs) x0
    last xs

A normal way to use macro is to use quasiquote paired with ~x and ~@xs to insert one or a span of items. Also notice that ~x is internally expanded to (~ x), so you can also use (~ x) and (~@ xs) as well:

defmacro if-not (condition true-branch ? false-branch)
  quasiquote $ if ~condition ~false-branch ~true-branch

To create new variables inside macro definitions, use (gensym) or (gensym |name):

defmacro case (item default & patterns)
  &let
    v (gensym |v)
    quasiquote
      &let (~v ~item)
        &case ~v ~default ~@patterns

Calcit was not designed to be identical to Clojure, so there are many details here and there.

Debug Macros

use macroexpand-all for debugging:

$ cr eval 'println $ format-to-cirru $ macroexpand-all $ quote $ let ((a 1) (b 2)) (+ a b)'

&let (a 1)
  &let (b 2)
    + a b

format-to-cirru and format-to-lisp are 2 custom code formatters:

$ cr eval 'println $ format-to-lisp $ macroexpand-all $ quote $ let ((a 1) (b 2)) (+ a b)'

(&let (a 1) (&let (b 2) (+ a b)))

The syntax macroexpand only expand syntax tree once:

$ cr eval 'println $ format-to-cirru $ macroexpand $ quote $ let ((a 1) (b 2)) (+ a b)'

&let (a 1)
  let
      b 2
    + a b