PS F:\learn\rustlearn> rustc learn1.rs PS F:\learn\rustlearn> .\learn1.exe 0.6823278038280194 PS F:\learn\rustlearn>

函數(shù)是一等公民，函數(shù)可作為函數(shù)的參數(shù)和返回值使用。
如下面代碼段所示

pub fn f_compute(com_fn:fn(f64)->f64,x:f64)->f64{com_fn(x) }

完整代碼如下：

use std::f64; pub fn get_next_x(x0:f64,x1:f64)->f64{let res1=&f_compute(fn1,x1);let res0=&f_compute(fn1,x0);x1-res1*((x1-x0)/(res1-res0)) } pub fn f_compute(com_fn:fn(f64)->f64,x:f64)->f64{com_fn(x) }pub fn fn1(x:f64)->f64{x.powi(3)+x-1.0_f64 }fn main() {let tol=1e-8_f64;let x0=0.0_f64;let x1=4.0_f64;let mut x_i:f64=x1;let mut x_isub1:f64=x0;let mut x_iplus1:f64;let mut ans:f64=0.0_f64; let mut finished=false;for _n in 1..200 {x_iplus1=get_next_x(x_isub1,x_i);if (x_iplus1-x_i).abs()<tol { ans=x_iplus1;finished=true;break;} x_isub1=x_i;x_i=x_iplus1;}if finished{println!("{}",ans); } } use std::f64; pub fn get_next_x(com_fn:fn(f64)->f64,x0:f64,x1:f64)->f64{let res1=&f_compute(com_fn,x1);let res0=&f_compute(com_fn,x0);x1-res1*((x1-x0)/(res1-res0)) } pub fn f_compute(com_fn:fn(f64)->f64,x:f64)->f64{com_fn(x) }pub fn fn1(x:f64)->f64{x.powi(3)+x-1.0_f64 } pub fn fn2(x:f64)->f64{2.98*x.powi(3)-5.21*x.powi(2)-7.6_f64 }fn main() {let tol=1e-8_f64;let x0=0.0_f64;let x1=4.0_f64;let mut x_i:f64=x1;let mut x_isub1:f64=x0;let mut x_iplus1:f64;let mut ans:f64=0.0_f64; let mut finished=false;for _n in 1..500 {x_iplus1=get_next_x(fn1,x_isub1,x_i);if (x_iplus1-x_i).abs()<tol { ans=x_iplus1;finished=true;break;} x_isub1=x_i;x_i=x_iplus1;}if finished{println!("{}",ans); }x_i=x1;x_isub1=x0;ans=0.0_f64; finished=false;for _n in 1..200 {x_iplus1=get_next_x(fn2,x_isub1,x_i);if (x_iplus1-x_i).abs()<tol { ans=x_iplus1;finished=true;break;} x_isub1=x_i;x_i=x_iplus1;}if finished{println!("{}",ans); } } PS F:\learn\rustlearn> rustc learn1.rs PS F:\learn\rustlearn> .\learn1.exe 0.6823278038280194 2.2514454804098265 PS F:\learn\rustlearn>

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