A set of three macros to ease writing `*.cljc` supporting Clojure, Clojurescript and self-hosted Clojurescript.
Because any macros problem can be solved by another level of macros, Macrovich is a set of four macros to ease writing *.cljc supporting Clojure, Clojurescript and self-hosted Clojurescript.
Excerpt from Being John Macrovich script:
Clojurescript >= 1.9.293 is required. This means Planck 2.0.0 or later is required. Lumo 1.0.0 is ok.
Add [net.cgrand/macrovich "0.2.1"] to your dependencies.
Macrovich exposes four macros:
* macros/deftime and macros/usetime to clearly demarcate regions of code that should be run in the macro-definition stage or in the macro-usage stage. (In Clojure there's no distinction; in pure Clojurescript it's easy: just wrap the first stage in #?(:clj ...) and the latter one in #?(:cljs ...); in self-hosted Clojurescript it's messy or everything gets evaluated twice; supporting the three at the same time is Macrovich's _raison d'être_.)
* macros/case is a macro to use instead of reader conditionals in macros or macros-supporting fns. This solves a problem with regular Clojurescript where macros are Clojure code and thus are read by taking the :clj branch of conditionals. So macros/case is like reader conditionals except the branch is picked at expansion time and not at definition time.
* macros/replace is a macro to avoid repeating similar reader conditionals, see https://github.com/cgrand/xforms/blob/d4f0280bb50d8cc53c3a5dfe24b17fe7701b4e43/src/net/cgrand/xforms.cljc#L276 for an example.
Below is a sample being-john.cljc file:
``clj
(ns being-john
#?(:clj
(:require [net.cgrand.macrovich :as macros])
:cljs
(:require-macros [net.cgrand.macrovich :as macros]
[net.cgrand.being :refer [add]]))) ; cljs must self refer macros
(macros/deftime
; anything inside a deftime block will only appear at the macro compilation stage.
(defmacro add
[a b]
(+ ~a ~b)))
(macros/usetime
; anything inside a usetime block will not appear at the macro compilation stage.
(defn sum
[a b]
(add a b)))
; anything outside these block is always visible as usual
``
case allows to select which form to emit in a macro based on the target language rather than the macro language. Consider these two macros:
`clj
(defmacro broken []
#?(:clj "clojure" :cljs "clojurescript"))
(defmacro correct []
(macros/case :clj "clojure" :cljs "clojurescript"))
; or
(defmacro correct []
(macros/case :clj "clojure" :cljs "clojurescript")) ; this works too, so no need to unquote in the middle of a syntax quotation and mess with gensyms
``
In regular (Clojure-hosted) Clojurescript (broken) expands to "clojure" while (correct) expands to "clojurescript"`.
The xforms lib has been converted to cljc:
* https://github.com/cgrand/xforms/blob/cljc/src/net/cgrand/xforms.cljc
* https://github.com/cgrand/xforms/blob/cljc/src/net/cgrand/xforms/rfs.cljc
* https://github.com/cgrand/xforms/blob/cljc/test/net/cgrand/xforms_test.clj
Copyright © 2016-2017 Christophe Grand
Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.