rust - Rust中的部分应用程序宏可以工作，但是

Question

因此，我正在编写(尝试)一些可变的宏，以尝试在 rust 中实现组合和 curry 。 pipe很简单。
可变参数部分应用了吗？没那么多。对任何可以为不使用那些令人讨厌的看似可忽略的类型args的部分应用程序宏提出解决方案的人(可能是可变参数？没有反射，我认为这是不可能的):

    //ltr compose for closures
macro_rules! pipe {
    ($init:tt |> $($fn:ident),+) => {{
        let mut r = $init;
        $( r = $fn(r); )*
        r
    }}
}

//partially apply a closure w/ up to 4 args
macro_rules! apply {
    ($fn:ident<$t1:ty,$t2:ty>($arg1:expr)) => {
        |x:$t2| $fn($arg1 as $t1, x)
    };
    ($fn:ident<$t1:ty,$t2:ty,$t3:ty>($arg1:expr)) => {
        |x:$t2, y:$t3| $fn($arg1 as $t1,x, y)
    };
    ($fn:ident<$t1:ty,$t2:ty,$t3:ty>($arg1:expr, $arg2:expr)) => {
        |x:$t3| $fn($arg1 as $t1,$arg2 as $t2,x)
    };
    ($fn:ident<$t1:ty,$t2:ty,$t3:ty,$t4:ty>($arg1:expr)) => {
        |x: $t2, y:$t3, z:$t4| $fn($arg1 as $t1, x, y, z)
    };
    ($fn:ident<$t1:ty,$t2:ty,$t3:ty,$t4:ty>($arg1:expr, $arg2:expr)) => {
        |x:$t3, y:$t4| $fn($arg1 as $t1,$arg2 as $t2, x, y)
    };
    ($fn:ident<$t1:ty,$t2:ty,$t3:ty,$t4:ty>($arg1:expr, $arg2:expr, $arg3:expr)) => {
        |x:$t4| $fn($arg1 as $t1,$arg2 as $t2,arg3 as $t3,x)
    };
}

fn main() {
    
 
    let add = |x:i32, y:i32| x + y;
    let sq = |x:i32| x * x;
    let dbl = |x:i32| x * 2;
    //blargh i hate those typeargs! i need them for the matcher
    //to get the original params number and type since rust has no reflection :(
    //weirdly if i ignore them with _ it works. But it will luckily fail
    //hard if you supply incorrect args.
    let plus1 = apply!(add<_,_>(1));
    
    let r = pipe!(3 |> dbl, plus1, sq);
    
    print!("{}", r);
}

编辑:我似乎无法对此执行可变参数的原因是因为这更改了闭包的结构。乍一看似乎不错，我只是将其包装在match语句中，该语句基于总参数以及exprs数量与总参数之间的差。但是如果您尝试在匹配臂中返回不同签名的闭包，则不会编译。好消息是这种方法的开销可能很低。但是，通过部分必要的内联闭包，对于部分应用程序确实不是一个很大的改进:

//simple, works, no type args or even type declarations on params I'm just a crazy person who wants it all!
let add = |x, y| x + y;
let add1 = |x| add(x, 1);

因此，这实际上只是学术上的追求，似乎不切实际

Answer 1

我不确定我是否理解您的问题，但是我认为也许这个库可以为您提供帮助:https://docs.rs/partial_application/0.2.0/partial_application/

#[macro_use]
extern crate partial_application;

//ltr compose for closures
macro_rules! pipe {
    ($init:tt |> $($fn:ident),+) => {{
        let mut r = $init;
        $( r = $fn(r); )*
        r
    }}
}

fn main() {


    let add = |x:i32, y:i32| x + y;
    let sq = |x:i32| x * x;
    let dbl = |x:i32| x * 2;
    //blargh i hate those typeargs! i need them for the matcher
    //to get the original params number and type since rust has no reflection :(
    //weirdly if i ignore them with _ it works. But it will luckily fail
    //hard if you supply incorrect args.
    let plus1 = partial!(add => 1,_);
    let r = pipe!(3 |> dbl, plus1, sq);

    print!("{}", r);
}

您可以引用此库来创建自己的宏。