Clojure: apply vs reduce for converting integers to chars and strings -

both of below functions return same output, first 1 uses reduce , pair of quote marks achieve same thing. played code , if delete "" marks, first character in sequence not converted it's integer value. second 1 seems clear me, feel first way superior, because packages of desired effects single function literal. unpack anonymous function me explain variables % , %2 referring , tell me why need "" first integer (115) in vector?

 (reduce #(str % (char %2)) ""             [115 101 99 114 101 116 32 109 101 115 115 97 103 101 115])   (apply str (map #(char %) [115 101 99 114 101 116 32 109 101 115 115 97 103 101 115])) 

the first function taken clojure cookbook discussion on int str conversion, here.

you can find anonymous function reader macro here

anonymous function literal (#())

#(...) => (fn [args] (...)) 

where args determined presence of argument literals taking form %, %n or %&. % synonym %1, %n designates nth arg (1-based), , %& designates rest arg. not replacement fn - idiomatic used short one-off mapping/filter fns , like. #() forms cannot nested.

% or %1 refers first argument , %2 refers second.

in case, in first approach, % refers "" , %2 refers vector of integers; in second approach, % vector of integers.

as difference between reduce , apply here, reduce provides supplied val, , in case "". without "", reduce call str 115 , (char 101), produce "115e". instead of calling str first , second element in vector, should call str empty string , first element of vector, produce "s". , in next reduce loop, str called parameter "s" , 101, yielding "se", , on.

and apply call, you've mapped char vector of integer before call apply, parameter of apply be: 1. function str; 2.a vector of characters function map produced.

also, can check out more information differences between apply , reduce in this question.