Struct ExternMap 

pub struct ExternMap { /* private fields */ }

HashMap-backed Externs impl for host-side Rust closures.

use flow_ir_core::{eval_expr_with_externs, EvalError, Expr, ExternMap};
use serde_json::{json, Value};

let mut externs = ExternMap::new();
externs.register("math.sqrt", |args: &[Value]| {
    let x = args[0].as_f64().ok_or_else(|| EvalError::ExternError {
        ref_: "math.sqrt".into(),
        msg: "expected number".into(),
    })?;
    Ok(json!(x.sqrt()))
});

let expr: Expr = serde_json::from_value(json!({
    "op": "call_extern", "ref": "math.sqrt",
    "args": [{ "op": "lit", "value": 9.0 }],
})).unwrap();
let out = eval_expr_with_externs(&expr, &json!({}), &externs).unwrap();
assert_eq!(out, json!(3.0));

Implementations

impl ExternMap

pub fn new() -> ExternMap

Create an empty registry.

pub fn register<F>(&mut self, name: impl Into<String>, f: F)

where F: Fn(&[Value]) -> Result<Value, EvalError> + Send + Sync + 'static,

Register a pure function under name (overwrites an existing entry).

pub fn contains(&self, name: &str) -> bool

Whether name is registered (compile-time whitelist check parity).

Trait Implementations

impl Default for ExternMap

fn default() -> ExternMap

Returns the “default value” for a type.

impl Externs for ExternMap

fn call(&self, ref_: &str, args: &[Value]) -> Result<Value, EvalError>

Invoke the extern registered under ref_ with already-evaluated args. Unregistered refs raise EvalError::ExternError.