我本以为以下代码可以工作:
```python # 代码示例 ```
但实际上它并不能正常运行。
```python # 代码示例 ```
但实际上它并不能正常运行。
use std::num::{Num};
use std::fmt::{Show};
pub type GradFn<T : Num> = for<'a> fn(&'a [T]) -> (T, Vec<T>);
fn minimize<T : Show, F>(f : GradFn<T>, x0 : &[T]) {
// some no-op to test types
print!("{}",f(x0))
}
fn main() {
let xSquared : GradFn<f64> = |x : &[f64]| -> (f64, Vec<f64>) {
return (x[0] * x[0], vec![2.0 * x[0]]);
};
let (fx, grad) = xSquared(vec![2.0f64].as_slice());
print!("{}", fx);
}
但是我得到了一个编译错误(见这里):
<anon>:12:32: 14:4 error: mismatched types: expected `fn(&'a [f64]) -> (f64, collections::vec::Vec<f64>)`, found `|&[f64]| -> (f64, collections::vec::Vec<f64>)` (expected extern fn, found fn)
<anon>:12 let xSquared : GradFn<f64> = |x : &[f64]| -> (f64, Vec<f64>) {
<anon>:13 return (x[0] * x[0], vec![2.0 * x[0]]);
<anon>:14 };