而非輪詢。非同步的 Python 程式需要「迴圈（loop）」來處理，類似於 Rust 的執行環境。 • JavaScript 的 Promise 也是類似的概念，但仍是基於回呼函數。JavaScript 的語言執行環境實 作了事件迴圈（event loop），所以隱藏了很多關於 Promise 的處理細節。 63.1 async/await 從高層次的角度來看，非同步的 Rust 程式碼看起來很像「一般的」同步程式碼： 因此大部分有趣的非同步作業皆無法在 Playground 中執行。 • 除非接受執行器輪詢，否則 Future 不會執行任何作業 (甚至不會啟動 I/O 作業)，因此 Future 是 「惰性」的。這一點與 JS Promise 不同。舉例來說，後者即使從未使用過，仍會執行至完成為止。 63.3.1 Tokio Tokio 提供以下項目： • 執行非同步程式碼的多執行緒執行階段。 • 標準程式庫的非同步版本。 • 作的功能類似於獨立的執行作業執行緒。 • 會合 • 選取 64.1 加入 會合作業會等待整個 Future 集合準備就緒，然後蒐集多個結果一次回傳。這類似於 JavaScript 中的 Promise.all 或 Python 中的 asyncio.gather。 use anyhow::Result; use futures::future; use reqwest; use std::

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } } Completeness of analysis The analyzer only looks at local information. In particular

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } } Completeness of analysis The analyzer only looks at local information. In particular

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } } Completeness of analysis The analyzer only looks at local information. In particular

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } } Completeness of analysis The analyzer only looks at local information. In particular

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } } Completeness of analysis The analyzer only looks at local information. In particular

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } }CHAPTER 106. DOCUMENTATION OF JULIA'S INTERNALS 1974 Completeness of analysis

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } } Completeness of analysis The analyzer only looks at local information. In particular

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } } Completeness of analysis The analyzer only looks at local information. In particular

results. This corresponds to the -ffast-math option of clang. • Write @simd in front of for loops to promise that the iterations are independent and may be re- ordered. Note that in many cases, Julia can automatically JL_DLLEXPORT jl_value_t *jl_apply_array_type(jl_value_t *type, size_t dim) JL_ALWAYS_LEAFTYPE; JL_GC_PROMISE_ROOTED This is a function-like annotation. Any value passed to this annotation will be considered happen to know for complicated external reasons // that val is rooted under these conditions JL_GC_PROMISE_ROOTED(val); } } Completeness of analysis The analyzer only looks at local information. In particular