Off the top of my head, I'd take out the "&" in front of the "|x|"
everywhere, it seems like you are borrowing a pointer out of something that
is already a borrowed pointer to a function (expected &, found &&, you have
one & too many, right? :-).
On Sun, Oct 27, 2013 at 2:15 PM, Ramakrishnan Muthukrishnan <
vu3...@gmail.com> wrote:
> I am having a hard time trying to figure out what is going on here.
>
> fn ntimes(f: &fn(int) -> int, n: int) -> &fn(int) -> int {
> match n {
> 0 => &|x| { x },
> _ => &|x| { f(x) },
> _ => &|x|
> {
> let nf = ntimes(f, n - 1);
> nf(f(x))
> },
> }
> }
>
> fn double(a: int) -> int {
> a * 2
> }
>
> fn main() {
> let quadruple = ntimes(double, 2);
> println(format!("quad = {:d}", quadruple(2)));
> }
>
> When I compile it, I get this error message:
>
> $ rustc --version
> rustc 0.9-pre (950add4 2013-10-26 02:16:08 -0700)
> host: x86_64-apple-darwin
>
> $ rustc fn1.rs
> fn1.rs:2:4: 10:5 error: mismatched types: expected
> `&fn<no-bounds>(int) -> int` but found `&&fn<no-bounds>(int) -> int`
> (expected fn but found &-ptr)
> fn1.rs:2 match n {
> fn1.rs:3 0 => &|x| { x },
> fn1.rs:4 _ => &|x| { f(x) },
> fn1.rs:5 _ => &|x|
> fn1.rs:6 {
> fn1.rs:7 let nf = ntimes(f, n - 1);
> ...
> error: aborting due to previous error
> task '<unnamed>' failed at 'explicit failure',
> /Users/rkrishnan/src/rust/src/libsyntax/diagnostic.rs:101
> task '<unnamed>' failed at 'explicit failure',
> /Users/rkrishnan/src/rust/src/librustc/rustc.rs:396
>
> Can someone help me understand what is going on here? I tried omitting
> the return type of ntimes and let compiler try to infer the type. The
> only change is in the first line of the code omitting the return type
> of ntimes. But I then get an error about quadruple function. It says
> that quadruple is a void.
>
> Thanks.
> --
> Ramakrishnan
> _______________________________________________
> Rust-dev mailing list
> Rust-dev@mozilla.org
> https://mail.mozilla.org/listinfo/rust-dev
>
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