[英]Simpler way to check if string start with a digit in Rust?
What I am currently using is this我目前使用的是这个
fn main() {
let a = "abc123";
let b = "1a2b3c";
println!("{}", a[0..1].chars().all(char::is_numeric));
println!("{}", b[0..1].chars().all(char::is_numeric));
}
Are there a more idiomatic and/or simpler way to do this?有没有更惯用和/或更简单的方法来做到这一点?
Note: The string is guaranteed to be non empty and made of ASCII characters.注意:字符串保证为非空且由 ASCII 字符组成。
If you are sure that it is non-empty and made out of ascii, you can operate directly on bytes ( u8
):如果您确定它是非空的并且由 ascii 制成,则可以直接对字节( u8
)进行操作:
a.as_bytes()[0].is_ascii_digit()
or或者
(b'0'..=b'9').contains(&a.as_bytes()[0])
More general setting (and, in my opinion , more idiomatic):更一般的设置(在我看来,更惯用):
a.chars().next().unwrap().is_numeric()
The reason all this looks a bit unwieldy is that there may be some things going wrong (that are easily overlooked in other languages):这一切看起来有点笨拙的原因是可能有一些事情出错(在其他语言中很容易被忽略):
Option
/ unwrap
-land字符串可能为空 => 引导我们进入Option
/ unwrap
-land Starting from your original solution and parse
:从您的原始解决方案开始并parse
:
fn main() {
let a = "abc123";
let b = "1a2b3c";
println!("{:?}", a[0..1].parse::<u8>().is_ok()); // false
println!("{:?}", b[0..1].parse::<u8>().is_ok()); // true
}
The string is guaranteed to be non empty.该字符串保证为非空。
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