Does Clojure specify the order of evaluation of function arguments?
I.e. When I call a function in Clojure:
(my-func (fun1 arg1) (fun2 arg2) (fun3 arg3))
Is the order of evaluation of fun1, fun2, and fun3 defined?
I understand that Java defines the order of evaluation of function arguments as left to right, but I can imagine a functional language like Clojure being more relaxed.
Order of evaluation is left to right. See http://clojure.org/evaluation
Both the operator and the operands (if any) are evaluated, from left to right.
((fun1 arg) (fun2 arg) (fun3 arg)) will cause all funN functions to be called, prior to the result of (fun1 arg) being cast to a function type (which it might not be).Left to right, but inside out as well (fun1 (fun2 arg2)).
I think that in general for a functional language, you would want to avoid the situation where (fun1 arg1) influences (fun2 arg2) or (fun3 arg3). (fun1 arg1) ideally would return a value without altering the state of existing data structures in your program.
Therefore, depending on how close you keep to a functional programming style, the left-to-right order of evaluation is unimportant.
(my-func (fun1 arg1) (fun2 arg2) (fun3 arg3))
my-func has arity of 3. The result of (fun1 arg1) will be passed as the first argument to my-func. Etc. Then my-func will be executed.
Therefore the order of evaluation of arguments to my-func does not matter at all.
If you have side-effects, then, well, hmmmm... But this answer does not change. The order does not matter.
Cheers -
