diff options
Diffstat (limited to 'src/libcore')
| -rw-r--r-- | src/libcore/result.rs | 46 |
1 files changed, 0 insertions, 46 deletions
diff --git a/src/libcore/result.rs b/src/libcore/result.rs index 0dc4fb83965..16798c039ba 100644 --- a/src/libcore/result.rs +++ b/src/libcore/result.rs @@ -227,52 +227,6 @@ //! ``` //! //! `try!` is imported by the prelude, and is available everywhere. -//! -//! # `Result` and `Option` -//! -//! The `Result` and [`Option`](../option/index.html) types are -//! similar and complementary: they are often employed to indicate a -//! lack of a return value; and they are trivially converted between -//! each other, so `Result`s are often handled by first converting to -//! `Option` with the [`ok`](type.Result.html#method.ok) and -//! [`err`](type.Result.html#method.ok) methods. -//! -//! Whereas `Option` only indicates the lack of a value, `Result` is -//! specifically for error reporting, and carries with it an error -//! value. Sometimes `Option` is used for indicating errors, but this -//! is only for simple cases and is generally discouraged. Even when -//! there is no useful error value to return, prefer `Result<T, ()>`. -//! -//! Converting to an `Option` with `ok()` to handle an error: -//! -//! ``` -//! use std::io::Timer; -//! let mut t = Timer::new().ok().expect("failed to create timer!"); -//! ``` -//! -//! # `Result` vs. `panic!` -//! -//! `Result` is for recoverable errors; `panic!` is for unrecoverable -//! errors. Callers should always be able to avoid panics if they -//! take the proper precautions, for example, calling `is_some()` -//! on an `Option` type before calling `unwrap`. -//! -//! The suitability of `panic!` as an error handling mechanism is -//! limited by Rust's lack of any way to "catch" and resume execution -//! from a thrown exception. Therefore using panics for error -//! handling requires encapsulating code that may panic in a task. -//! Calling the `panic!` macro, or invoking `panic!` indirectly should be -//! avoided as an error reporting strategy. Panics is only for -//! unrecoverable errors and a panicking task is typically the sign of -//! a bug. -//! -//! A module that instead returns `Results` is alerting the caller -//! that failure is possible, and providing precise control over how -//! it is handled. -//! -//! Furthermore, panics may not be recoverable at all, depending on -//! the context. The caller of `panic!` should assume that execution -//! will not resume after the panic, that a panic is catastrophic. #![stable] |