Created
April 12, 2016 14:54
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#![feature(trace_macros)] | |
#![feature(log_syntax)] | |
//trace_macros!(true); | |
macro_rules! id {($e : expr) => ($e)} | |
macro_rules! vecc {($($t:tt)*) => (Vecc{v:vec!($($t)*)})} | |
macro_rules! mdo { | |
//{{$(let $pat : pat = $expr : expr;)+}; $($rest : tt)*} => ({let $pat = $expr; mdo!{$($rest)*}}); | |
{{let $($rst : tt)+}; $($rest : tt)*} => (id!({let $($rst)+ mdo!{$($rest)*}})); | |
{$x : expr} => ($x); | |
//{$pat : pat = $b : expr; $x : expr} => ($b.and_then(|$pat| $x)); | |
{ $pat : pat = $b : expr; $($b1 : tt)+} => ($b.and_then(|$pat| mdo!{$($b1)+ })) | |
} | |
//trait Unit[M<_>] { fn unit<T>(T) -> M<T>; } | |
#[derive(Debug)] | |
struct Vecc<T>{v: Vec<T>} | |
impl<T> Vecc<T> { | |
pub fn new() -> Vecc<T> {Vecc{v: Vec::new()}} | |
fn push(&mut self, value: T) {self.v.push(value)} | |
pub fn and_then<U, F: Fn(&T) -> Vecc<U>>(&self, f : F) -> Vecc<U> { | |
let mut out = Vecc::new(); | |
for x in &self.v { | |
for y in f(x).v { | |
out.push(y); | |
} | |
} | |
out | |
} | |
} | |
fn main() { | |
fn sq(x: u32) -> Option<u32> { Some(x * x) } | |
fn nope(_: u32) -> Option<u32> { None } | |
let v : Vecc<(i32,i32)> = mdo!{a = vecc!(1,2); b = vecc!(3,4); vecc!((*a,*b))}; | |
println!("{:?}", v); | |
let _ : Result<i32,i32> = mdo!{a = Ok(3); b = Ok(a); {println!("{}",a+b);Ok(b+a)}}; | |
let _ : Option<u32> = mdo!{{let nn = Some(2);}; n = nn; m = sq(n); Some(m)}; | |
assert_eq!(mdo!{n = Some(2); m = sq(n); sq(m)}, Some(16)); | |
assert_eq!(mdo!{a = Some(2); a = sq(a); sq(a)}, Some(16)); | |
assert_eq!(mdo!{a = Some(2); a = sq(a); nope(a)}, None); | |
assert_eq!(mdo!{a = Some(2); a = nope(a); sq(a)}, None); | |
assert_eq!(mdo!{a = None; a = sq(a); sq(a)}, None); | |
} |
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