CODEWITHSUNDEEP
compiler-errorsrust
Kazik
Kazik

Reputation: 45

"type annotations required" while using RustFFT

I have a problem with the following code

extern crate num;
extern crate rustfft;

use rustfft::num_complex::Complex;
use rustfft::num_traits::Zero;

pub fn ct_fft(input: &Vec<f64>, sampling: u32) {
    let data_size = input.len();

    let mut input_array: Vec<Complex<f64>> = Vec::with_capacity(data_size);

    let fft = rustfft::FFTplanner::new(false).plan_fft(data_size as usize);

    for v in input {
        input_array.push(Complex { re: *v, im: 0.0 });
    }
}

I get the error:

error[E0283]: type annotations required: cannot resolve `_: rustfft::FFTnum`
  --> src/ctdsp.rs:19:15
   |
19 |     let fft = rustfft::FFTplanner::new(false).plan_fft(data_size as usize);
   |               ^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: required by `<rustfft::FFTplanner<T>>::new`

error: aborting due to previous error

I don't understand why I got this error; I was using RustFFT earlier and it worked with no problems and I'm using it exactly the same way. I cannot find any information about this error in regard to RustFFT.



Rust version:

╰─$ rustc --version                                                                               
rustc 1.26.0-nightly (9c9424de5 2018-03-27)

Upvotes: 1

Views: 285

Answers (1)

DK.
DK.

Reputation: 59125

The problem (from your comments) is that you weren't using fft. Rust can infer types, but it can only do so if there's enough context. If you never use fft, the compiler doesn't have enough information to work out what the complete type is supposed to be.

Remember, every variable in Rust has a single, complete type. It's just that in some cases, Rust can work it out by itself and lets you omit the type. This is not one of those cases.

Upvotes: 1

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