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use quote::{quote_spanned, ToTokens};
use syn::parse_quote;
use super::{
DelayType, OperatorCategory, OperatorConstraints, OperatorInstance,
OperatorWriteOutput, PortIndexValue, WriteContextArgs, RANGE_0, RANGE_1,
};
/// > 2 input streams of the same type T, 1 output stream of type T
///
/// Forms the set difference of the items in the input
/// streams, returning items in the `pos` input that are not found in the
/// `neg` input.
///
/// `difference` can be provided with one or two generic lifetime persistence arguments
/// in the same way as [`join`](#join), see [`join`'s documentation](#join) for more info.
///
/// Note multiset semantics here: each (possibly duplicated) item in the `pos` input
/// that has no match in `neg` is sent to the output.
///
/// ```hydroflow
/// source_iter(vec!["cat", "cat", "elephant", "elephant"]) -> [pos]diff;
/// source_iter(vec!["cat", "gorilla"]) -> [neg]diff;
/// diff = difference_multiset() -> assert_eq(["elephant", "elephant"]);
/// ```
pub const DIFFERENCE_MULTISET: OperatorConstraints = OperatorConstraints {
name: "difference_multiset",
categories: &[OperatorCategory::MultiIn],
hard_range_inn: &(2..=2),
soft_range_inn: &(2..=2),
hard_range_out: RANGE_1,
soft_range_out: RANGE_1,
num_args: 0,
persistence_args: &(0..=2),
type_args: RANGE_0,
is_external_input: false,
has_singleton_output: false,
ports_inn: Some(|| super::PortListSpec::Fixed(parse_quote! { pos, neg })),
ports_out: None,
input_delaytype_fn: |idx| match idx {
PortIndexValue::Path(path) if "neg" == path.to_token_stream().to_string() => {
Some(DelayType::Stratum)
}
_else => None,
},
write_fn: |wc @ &WriteContextArgs {
op_span,
ident,
inputs,
op_inst: OperatorInstance { .. },
..
},
diagnostics| {
let OperatorWriteOutput {
write_prologue,
write_iterator,
write_iterator_after,
} = (super::anti_join_multiset::ANTI_JOIN_MULTISET.write_fn)(wc, diagnostics)?;
let pos = &inputs[1];
let write_iterator = quote_spanned! {op_span=>
let #pos = #pos.map(|k| (k, ()));
#write_iterator
let #ident = #ident.map(|(k, ())| k);
};
Ok(OperatorWriteOutput {
write_prologue,
write_iterator,
write_iterator_after,
})
},
};