Passing redefined function as argument

[mortenpi]

The following code, where we pass a function as an argument, redefine it and pass it again,

q(n) = 0
@show map(q, 1:1)
q(n) = 1
@show map(q, 1:1)

doesn't work as expected on 0.5 and 0.6, outputting:

map(q,1:1) = [0]
WARNING: Method definition q(Any) in module Main at ...
map(q,1:1) = [0]

I am guessing it's due to #265 and the fact that every function is a separate type now.

However, unlike most of #265, it's a regression compared to 0.4, since there we get what we would expect:

map(q,1:1) = [0]
map(q,1:1) = [1]

Sorry if this has already been discussed, but I was not able to find any mention of this. I do feel that perhaps this is something that should be addressed in 0.5, since the regression makes REPL work a bit more tedious.

[yuyichao]

Dup of #265

[yuyichao]

And your case is discussed in #265 already #265 (comment)

[mortenpi]

Sorry, missed that. However, will the fix of #265 get backported to 0.5 as well? It only has the 0.6 milestone at the moment.

[yuyichao]

No this is unlikely going to be fixed in 0.5.

[mortenpi]

In that case I would maintain that it's somewhat of an annoying regression compared to 0.4 😞. At least for me the REPL workflow where I keep redefining functions in the global scope is pretty common.

[mortenpi]

Should it at least be mentioned in NEWS.md? And while there is a WARNING now, perhaps that could be made more informative, stating something along the lines of "already called/compiled functions using this function or receiving it as an argument, will still use the old definition and hence may not work as expected".

[tkelman]

sure. fastest way would be to propose a wording which we could iterate on in a PR

[cstjean]

Is there any work-around?

[iamed2]

The workaround would be to use anonymous functions:

julia> q(n) = 0
q (generic function with 1 method)

julia> map(x->q(x), 1:1)
1-element Array{Int64,1}:
 0

julia> q(n) = 1
WARNING: Method definition q(Any) in module Main at REPL[1]:1 overwritten at REPL[5]:1.
q (generic function with 1 method)

julia> map(x->q(x), 1:1)
1-element Array{Int64,1}:
 1