Clojure def vs defn for a function with no arguments
I have written a program in clojure but some of the functions have no arguments. What would be the advantages of coding such functions as a "def" instead of a "defn" with no arguments?
def s are evaluated only once whereas defn s (with or without arguments) are evaluated (executed) every time they are called. So if your functions always return the same value, you can change them to def s but not otherwise.
user=> (def t0 (System/currentTimeMillis))
user=> (defn t1 [] (System/currentTimeMillis))
user=> (t1)
1318408717941
user=> t0
1318408644243
user=> t0
1318408644243
user=> (t1)
1318408719361
（defn name ...）只是一个变成（def name（fn ...）的宏，不管它有多少个参数，所以它只是一个快捷方式，详见（doc defn）。
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