On May 4, 2016, at 5:28 PM, Johannes <[email protected]> wrote:
> Maybe you are right. But I've deliberately given function objects to eval
> often without any problems until I used functions of some special kind. I do
> not understand why the behavior for the 2 versions of the function f- I've
> shown is different.
Oops, I think I missed the main problem: you were passing a pre-evaluated map
object directly to eval. What eval really wants is the kind of thing that the
reader returns after it reads a string. The reader doesn’t evaluate symbols,
like f-. That’s eval’s job. When the reader sees the string f-, it returns the
symbol f-. You passed eval the actual function object, not the symbol f-. Eval
wants to see the symbol; it will replace it with the object that it evaluates
to.
In other words, I think you just forgot to quote the expressions that you were
passing to eval. Adding the quote, here’s what I get:
user=> (def f- (let [v 1
#_=> f (fn [x] v)] f))
#'user/f-
user=> (eval '{:d f-})
{:d #function[user/fn--10235/f--10236]}
user=> (def f- (let [v 1
#_=> f (fn [x] x)] f))
#'user/f-
user=> (eval '{:d f-})
{:d #function[user/fn--10243/f--10244]}
--
Ben Kovitz
http://mypage.iu.edu/~bkovitz/
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