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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.//!  This example shows you how to define ops in Rust and then call them from//!  JavaScript.
use deno_core::op;use deno_core::Extension;use deno_core::JsRuntime;use deno_core::RuntimeOptions;
// This is a hack to make the `#[op]` macro work with// deno_core examples.// You can remove this:use deno_core::*;
#[op]fn op_sum(nums: Vec<f64>) -> Result<f64, deno_core::error::AnyError> {  // Sum inputs  let sum = nums.iter().fold(0.0, |a, v| a + v);  // return as a Result<f64, AnyError>  Ok(sum)}
fn main() {  // Build a deno_core::Extension providing custom ops  let ext = Extension::builder()    .ops(vec![      // An op for summing an array of numbers      // The op-layer automatically deserializes inputs      // and serializes the returned Result & value      op_sum::decl(),    ])    .build();
  // Initialize a runtime instance  let mut runtime = JsRuntime::new(RuntimeOptions {    extensions: vec![ext],    ..Default::default()  });
  // Now we see how to invoke the op we just defined. The runtime automatically  // contains a Deno.core object with several functions for interacting with it.  // You can find its definition in core.js.  runtime    .execute_script(      "<usage>",      r#"// Print helper function, calling Deno.core.print()function print(value) {  Deno.core.print(value.toString()+"\n");}
const arr = [1, 2, 3];print("The sum of");print(arr);print("is");print(Deno.core.ops.op_sum(arr));
// And incorrect usagetry {  print(Deno.core.ops.op_sum(0));} catch(e) {  print('Exception:');  print(e);}"#,    )    .unwrap();}