polydat-nodes 0.3.1

Polydat node library: hashing, sampling, strings, encodings, noise, vectors, and more
Documentation 
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// Copyright 2024-2026 Jonathan Shook
// SPDX-License-Identifier: Apache-2.0

//! The producer node (SRD 113 ยง3.1). `name := for ...` lowers to
//! `const name := streamer("<json>")`, where the payload is the
//! resolved comprehension serialized by [`StreamerValue::to_json`].
//! The node parses once at setup and emits the same reflected value on
//! every pull, so the wire is an init-time constant.

use polydat::derive_support::Ext;
use polydat::iteration::comprehension::streamer_value::StreamerValue;

/// Materialize a comprehension as a `Streamer` value. Authors do not
/// call this directly; the compiler emits it for `for` expressions.
#[polydat::polydat_node(category = Variadic)]
fn streamer(
    spec: Const<&str>,
    #[poly_const(StreamerValue::from_json, from = spec)] parsed: &StreamerValue,
) -> Ext<StreamerValue> {
    Ext(parsed.clone())
}

#[cfg(test)]
mod tests {
    use super::*;
    use polydat::ast::{PolydatNode, Value};
    use polydat::iteration::comprehension::ast::Comprehension;
    use polydat::iteration::comprehension::source::Source;

    #[test]
    fn node_round_trips_the_payload() {
        let ast = Comprehension::clause(
            "k",
            Source::IntRange {
                lo: 1,
                hi: 4,
                step: 1,
            },
        );
        let payload = StreamerValue::new("k in 1..4", ast).to_json();
        let node = Streamer::new(payload);
        let mut out = [Value::None];
        node.eval(&[], &mut out);
        let s = out[0].as_streamer().expect("streamer value");
        assert_eq!(s.text, "k in 1..4");
        assert_eq!(s.element_names(), vec!["k"]);
    }
}