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use quote::{quote_spanned, ToTokens};
use super::{
OperatorCategory, OperatorConstraints, OperatorWriteOutput,
WriteContextArgs, RANGE_0, RANGE_1, RANGE_ANY,
};
/// > *n* input streams of the same type, 1 output stream of the same type
///
/// Unions an arbitrary number of input streams into a single stream. Each input sequence is a subsequence of the output, but no guarantee is given on how the inputs are interleaved.
///
/// Since `union` has multiple input streams, it needs to be assigned to
/// a variable to reference its multiple input ports across statements.
///
/// ```dfir
/// source_iter(vec!["hello", "world"]) -> my_union;
/// source_iter(vec!["stay", "gold"]) -> my_union;
/// source_iter(vec!["don't", "give", "up"]) -> my_union;
/// my_union = union()
/// -> map(|x| x.to_uppercase())
/// -> assert_eq(["HELLO", "WORLD", "STAY", "GOLD", "DON'T", "GIVE", "UP"]);
/// ```
pub const UNION: OperatorConstraints = OperatorConstraints {
name: "union",
categories: &[OperatorCategory::MultiIn],
hard_range_inn: RANGE_ANY,
soft_range_inn: &(2..),
hard_range_out: RANGE_1,
soft_range_out: RANGE_1,
num_args: 0,
persistence_args: RANGE_0,
type_args: RANGE_0,
is_external_input: false,
has_singleton_output: false,
flo_type: None,
ports_inn: None,
ports_out: None,
input_delaytype_fn: |_| None,
write_fn: |&WriteContextArgs {
root,
op_span,
ident,
inputs,
outputs,
is_pull,
..
},
_| {
let write_iterator = if is_pull {
let chains = inputs
.iter()
.map(|i| i.to_token_stream())
.reduce(|a, b| quote_spanned! {op_span=> check_inputs(#a, #b) })
.unwrap_or_else(|| quote_spanned! {op_span=> #root::dfir_pipes::pull::empty() });
quote_spanned! {op_span=>
let #ident = {
#[allow(unused)]
#[inline(always)]
fn check_inputs<A, B, Item>(
a: A, b: B
) -> impl #root::dfir_pipes::pull::Pull<
Item = Item,
Meta = A::Meta,
CanPend = <A::CanPend as #root::dfir_pipes::Toggle>::Or<B::CanPend>,
CanEnd = B::CanEnd,
>
where
A: #root::dfir_pipes::pull::Pull<Item = Item, CanEnd = #root::dfir_pipes::Yes>,
B: #root::dfir_pipes::pull::Pull<Item = Item, Meta = A::Meta>,
{
// NOTE(mingwei): `merge` (allowing async interleaving) may make more sense, but also
// might inline worse. Merge may have correctness implications.
#root::dfir_pipes::pull::Pull::chain(
#root::dfir_pipes::pull::Pull::fuse(a),
b,
)
}
#chains
};
}
} else {
assert_eq!(1, outputs.len());
let output = &outputs[0];
quote_spanned! {op_span=>
let #ident = #output;
}
};
Ok(OperatorWriteOutput {
write_iterator,
..Default::default()
})
},
};