Macro pgrab 

macro_rules! pgrab {
    ($params:ident[$($kind:ident $path:tt),+]) => { ... };
    ($expr_head:ident $(. $expr_part:ident $( ( $($args:tt)* ) )? )+ [$($kind:ident $path:tt),+]) => { ... };
}

Grab an instantaneous snapshot of parameter values at the start of the buffer.

This has the same syntax as pzip! but instead of returning a per-sample iterator, it returns the values from the first sample as a tuple.

This is useful for parameters that don’t need to be modulated every sample.

Examples

let params = ConstantBufferStates::new_defaults(
  vec![
    StaticInfoRef {
      title: "Gain",
      short_title: "Gain",
      unique_id: "gain",
      flags: Default::default(),
      type_specific: TypeSpecificInfoRef::Numeric {
        default: 0.5,
        valid_range: 0.0..=1.0,
        units: None,
      },
    },
    StaticInfoRef {
      title: "Switch",
      short_title: "Switch",
      unique_id: "enabled",
      flags: Default::default(),
      type_specific: TypeSpecificInfoRef::Switch {
        default: true,
      },
    },
  ],
);

let (gain, enabled) = pgrab!(params[numeric "gain", switch "enabled"]);
assert_eq!(gain, 0.5);
assert_eq!(enabled, true);

It also works with a single parameter:

let params = ConstantBufferStates::new_defaults(
  vec![
    StaticInfoRef {
      title: "Gain",
      short_title: "Gain",
      unique_id: "gain",
      flags: Default::default(),
      type_specific: TypeSpecificInfoRef::Numeric {
        default: 0.75,
        valid_range: 0.0..=1.0,
        units: None,
      },
    },
  ],
);

let gain = pgrab!(params[numeric "gain"]);
assert_eq!(gain, 0.75);