fn identifier(input: &str) -> ParseResult<&str> {
    let (input, _) = space0(input)?;
    let (input, i) = take_while1(|input: char| input.is_alphanumeric() || input == '_')(input)?;
    let (input, _) = space0(input)?;
    Ok((input, i))
}
/// This parses an identifier, which is composed of alphanumeric characters and underscores.
/// identifiers can start with numbers.
This parses an identifier, which is composed of alphanumeric characters and underscores.
identifiers can start with numbers.
This parses an identifier which is composed of alphanumeric characters and underscores . identifiers can start with numbers .
fn identifier(input: &str) -> ParseResult<&str> {
    let (input, _) = space0(input)?;
    let (input, i) = take_while1(|input: char| input.is_alphanumeric() || input == '_')(input)?;
    let (input, _) = space0(input)?;
    Ok((input, i))
}
fn identifier ( input : & str ) -> ParseResult < & str > { let ( input , _ ) = space0 ( input ) ? ; let ( input , i ) = take_while1 ( | input : char | input . is_alphanumeric ( ) || input == '_' ) ( input ) ? ; let ( input , _ ) = space0 ( input ) ? ; Ok ( ( input , i ) ) }
This parses an identifier, which is composed of alphanumeric characters and underscores.
This parses an identifier which is composed of alphanumeric characters and underscores .
input
&str
input
&str