anaphoric-threading.clj

(defmacro <-> [expr-1 expr-2 & exprs]                    
  (let [expr-2-with-expr-1-let `(let ~['<- expr-1]       
                                  ~(if (seq? expr-2)     
                                     expr-2              
                                     `(~expr-2 ~'<-) ) )]
    (if exprs                                            
      `(<-> ~expr-2-with-expr-1-let ~@exprs)             
      expr-2-with-expr-1-let ) ) )                       
                                                         
;; Example                                               
(defn read-from-json-file [filename]                     
  (<-> filename                                          
       slurp                                             
       (j/read-str <- :key-fn keyword)                   
       (map #(update % :ts ts->datetime) <-) ) )