{"by":"wooby","id":8926982,"parent":8925690,"text":"This was a great example, and I think you are absolutely right that it\nis the identical in function, if not in form, to mine.<p>Interestingly, in the course of concocting a counter-counter example,\nI came up with this in an effort to show the two dynamic variables we\nstipulate - <i>host</i> and <i>target</i> - were absolutely required:<p><pre><code> #+clj\n (defmacro my-macro []\n (cond\n (contains? *features* :clj) `(some-clojure-thing)\n (contains? *features* :cljs) `~(do (require 'some-ns)\n ((resolve 'some-ns/some-fn)))))\n</code></pre>\nMy hope was to make the point that 'some-ns/some-fn would run in a\ncontext where (<i>features</i> :cljs) is true - as it is in the caller's\n(macro body) environment - which would result in the system attempting\nto run ClojureScript code, which would explode because the macro is\nClojure. Then I realized that require runs load, and load is in the\nmacro body. The load/require available in the environment is\nClojure-specific! Thus, load/require can bind disj :cljs and conj\n:clj before reading and compiling some-ns.<p>My counter-example failed, but did bring me a little closer to the\ntruth - that we only need one dynamic variable, <i>platform</i>. Any\nplatform that has the ability to load code also has an opportunity to\nbind <i>platform</i> and thereby inform macros of target. This simplifies\nthe Feature Macro proposal by half and we are excited to amend it.<p>Our updated cross-platform example becomes:<p><pre><code> (case-platform\n :cljs nil\n :clj (defmacro my-macro []\n (condp = *platform*\n :clj `(some-clojure-thing)\n :cljs `(some-cljs-thing))))\n</code></pre>\nInstead of <i>host</i> and <i>target</i>, we are down to just <i>platform</i>. We\ncontinue to see no need for a <i>features</i> set because of Clojure's\nplatform-symbiosis.","time":1421890422,"type":"comment"}