// option. This file may not be copied, modified, or distributed
// except according to those terms.
-/// Creates a `Vec` containing the arguments.
+/// Creates a [`Vec`] containing the arguments.
///
/// `vec!` allows `Vec`s to be defined with the same syntax as array expressions.
/// There are two forms of this macro:
///
-/// - Create a `Vec` containing a given list of elements:
+/// - Create a [`Vec`] containing a given list of elements:
///
/// ```
/// let v = vec![1, 2, 3];
/// assert_eq!(v[2], 3);
/// ```
///
-/// - Create a `Vec` from a given element and size:
+/// - Create a [`Vec`] from a given element and size:
///
/// ```
/// let v = vec![1; 3];
/// ```
///
/// Note that unlike array expressions this syntax supports all elements
-/// which implement `Clone` and the number of elements doesn't have to be
+/// which implement [`Clone`] and the number of elements doesn't have to be
/// a constant.
///
-/// This will use `clone()` to duplicate an expression, so one should be careful
+/// This will use `clone` to duplicate an expression, so one should be careful
/// using this with types having a nonstandard `Clone` implementation. For
/// example, `vec![Rc::new(1); 5]` will create a vector of five references
/// to the same boxed integer value, not five references pointing to independently
/// boxed integers.
+///
+/// [`Vec`]: ../std/vec/struct.Vec.html
+/// [`Clone`]: ../std/clone/trait.Clone.html
#[cfg(not(test))]
#[macro_export]
#[stable(feature = "rust1", since = "1.0.0")]
($($x:expr,)*) => (vec![$($x),*])
}
-/// Use the syntax described in `std::fmt` to create a value of type `String`.
-/// See [`std::fmt`][fmt] for more information.
+/// Creates a `String` using interpolation of runtime expressions.
+///
+/// The first argument `format!` recieves is a format string. This must be a string
+/// literal. The power of the formatting string is in the `{}`s contained.
+///
+/// Additional parameters passed to `format!` replace the `{}`s within the
+/// formatting string in the order given unless named or positional parameters
+/// are used, see [`std::fmt`][fmt] for more information.
+///
+/// A common use for `format!` is concatenation and interpolation of strings.
+/// The same convention is used with [`print!`] and [`write!`] macros,
+/// depending on the intended destination of the string.
///
/// [fmt]: ../std/fmt/index.html
+/// [`print!`]: macro.print.html
+/// [`write!`]: macro.write.html
///
/// # Panics
///
/// # Custom Messages
///
/// This macro has a second form, where a custom panic message can
-/// be provided with or without arguments for formatting.
+/// be provided with or without arguments for formatting. See [`std::fmt`]
+/// for syntax for this form.
///
/// [`panic!`]: macro.panic.html
/// [`debug_assert!`]: macro.debug_assert.html
-/// [testing]: ../book/first-edition/testing.html
+/// [testing]: ../book/second-edition/ch11-01-writing-tests.html#checking-results-with-the-assert-macro
+/// [`std::fmt`]: ../std/fmt/index.html
///
/// # Examples
///
/// On panic, this macro will print the values of the expressions with their
/// debug representations.
///
-/// Unlike `assert_eq!`, `debug_assert_eq!` statements are only enabled in non
+/// Unlike [`assert_eq!`], `debug_assert_eq!` statements are only enabled in non
/// optimized builds by default. An optimized build will omit all
/// `debug_assert_eq!` statements unless `-C debug-assertions` is passed to the
/// compiler. This makes `debug_assert_eq!` useful for checks that are too
/// expensive to be present in a release build but may be helpful during
/// development.
///
+/// [`assert_eq!`]: ../std/macro.assert_eq.html
+///
/// # Examples
///
/// ```
/// On panic, this macro will print the values of the expressions with their
/// debug representations.
///
-/// Unlike `assert_ne!`, `debug_assert_ne!` statements are only enabled in non
+/// Unlike [`assert_ne!`], `debug_assert_ne!` statements are only enabled in non
/// optimized builds by default. An optimized build will omit all
/// `debug_assert_ne!` statements unless `-C debug-assertions` is passed to the
/// compiler. This makes `debug_assert_ne!` useful for checks that are too
/// expensive to be present in a release build but may be helpful during
/// development.
///
+/// [`assert_ne!`]: ../std/macro.assert_ne.html
+///
/// # Examples
///
/// ```
/// Helper macro for reducing boilerplate code for matching `Result` together
/// with converting downstream errors.
///
-/// Prefer using `?` syntax to `try!`. `?` is built in to the language and is
-/// more succinct than `try!`. It is the standard method for error propagation.
+/// The `?` operator was added to replace `try!` and should be used instead.
///
-/// `try!` matches the given `Result`. In case of the `Ok` variant, the
+/// `try!` matches the given [`Result`]. In case of the `Ok` variant, the
/// expression has the value of the wrapped value.
///
/// In case of the `Err` variant, it retrieves the inner error. `try!` then
/// error is then immediately returned.
///
/// Because of the early return, `try!` can only be used in functions that
-/// return `Result`.
+/// return [`Result`].
+///
+/// [`Result`]: ../std/result/enum.Result.html
///
/// # Examples
///
/// }
/// }
///
+/// // The prefered method of quick returning Errors
+/// fn write_to_file_question() -> Result<(), MyError> {
+/// let mut file = File::create("my_best_friends.txt")?;
+/// Ok(())
+/// }
+///
+/// // The previous method of quick returning Errors
/// fn write_to_file_using_try() -> Result<(), MyError> {
/// let mut file = try!(File::create("my_best_friends.txt"));
/// try!(file.write_all(b"This is a list of my best friends."));
-/// println!("I wrote to the file");
/// Ok(())
/// }
+///
/// // This is equivalent to:
/// fn write_to_file_using_match() -> Result<(), MyError> {
/// let mut file = try!(File::create("my_best_friends.txt"));
/// Ok(v) => v,
/// Err(e) => return Err(From::from(e)),
/// }
-/// println!("I wrote to the file");
/// Ok(())
/// }
/// ```
/// formatted according to the specified format string and the result will be passed to the writer.
/// The writer may be any value with a `write_fmt` method; generally this comes from an
/// implementation of either the [`std::fmt::Write`] or the [`std::io::Write`] trait. The macro
-/// returns whatever the 'write_fmt' method returns; commonly a [`std::fmt::Result`], or an
+/// returns whatever the `write_fmt` method returns; commonly a [`std::fmt::Result`], or an
/// [`io::Result`].
///
/// See [`std::fmt`] for more information on the format string syntax.
/// * Loops that dynamically terminate.
/// * Iterators that dynamically terminate.
///
+/// If the determination that the code is unreachable proves incorrect, the
+/// program immediately terminates with a [`panic!`]. The function [`unreachable`],
+/// which belongs to the [`std::intrinsics`] module, informs the compilier to
+/// optimize the code out of the release version entirely.
+///
+/// [`panic!`]: ../std/macro.panic.html
+/// [`unreachable`]: ../std/intrinsics/fn.unreachable.html
+/// [`std::intrinsics`]: ../std/intrinsics/index.html
+///
/// # Panics
///
-/// This will always [panic!](macro.panic.html)
+/// This will always [`panic!`]
///
+/// [`panic!`]: ../std/macro.panic.html
/// # Examples
///
/// Match arms:
});
}
-/// A standardized placeholder for marking unfinished code. It panics with the
-/// message `"not yet implemented"` when executed.
+/// A standardized placeholder for marking unfinished code.
+///
+/// It panics with the message `"not yet implemented"` when executed.
///
/// This can be useful if you are prototyping and are just looking to have your
/// code typecheck, or if you're implementing a trait that requires multiple
/// methods, and you're only planning on using one of them.
///
+/// # Panics
+///
+/// This macro always panics.
+///
/// # Examples
///
/// Here's an example of some in-progress code. We have a trait `Foo`:
/// The entry point for panic of Rust threads.
///
+/// This allows a program to to terminate immediately and provide feedback
+/// to the caller of the program. `panic!` should be used when a program reaches
+/// an unrecoverable problem.
+///
+/// This macro is the perfect way to assert conditions in example code and in
+/// tests. `panic!` is closely tied with the `unwrap` method of both [`Option`]
+/// and [`Result`][runwrap] enums. Both implementations call `panic!` when they are set
+/// to None or Err variants.
+///
/// This macro is used to inject panic into a Rust thread, causing the thread to
/// panic entirely. Each thread's panic can be reaped as the `Box<Any>` type,
/// and the single-argument form of the `panic!` macro will be the value which
/// is transmitted.
///
+/// [`Result`] enum is often a better solution for recovering from errors than
+/// using the `panic!` macro. This macro should be used to avoid proceeding using
+/// incorrect values, such as from external sources. Detailed information about
+/// error handling is found in the [book].
+///
/// The multi-argument form of this macro panics with a string and has the
-/// `format!` syntax for building a string.
+/// [`format!`] syntax for building a string.
+///
+/// [runwrap]: ../std/result/enum.Result.html#method.unwrap
+/// [`Option`]: ../std/option/enum.Option.html#method.unwrap
+/// [`Result`]: ../std/result/enum.Result.html
+/// [`format!`]: ../std/macro.format.html
+/// [book]: ../book/second-edition/ch09-01-unrecoverable-errors-with-panic.html
///
/// # Current implementation
///
/// Macro for printing to the standard output.
///
-/// Equivalent to the `println!` macro except that a newline is not printed at
+/// Equivalent to the [`println!`] macro except that a newline is not printed at
/// the end of the message.
///
/// Note that stdout is frequently line-buffered by default so it may be
-/// necessary to use `io::stdout().flush()` to ensure the output is emitted
+/// necessary to use [`io::stdout().flush()`][flush] to ensure the output is emitted
/// immediately.
///
/// Use `print!` only for the primary output of your program. Use
-/// `eprint!` instead to print error and progress messages.
+/// [`eprint!`] instead to print error and progress messages.
+///
+/// [`println!`]: ../std/macro.println.html
+/// [flush]: ../std/io/trait.Write.html#tymethod.flush
+/// [`eprint!`]: ../std/macro.eprint.html
///
/// # Panics
///
($($arg:tt)*) => ($crate::io::_print(format_args!($($arg)*)));
}
-/// Macro for printing to the standard output, with a newline. On all
-/// platforms, the newline is the LINE FEED character (`\n`/`U+000A`) alone
+/// Macro for printing to the standard output, with a newline.
+///
+/// On all platforms, the newline is the LINE FEED character (`\n`/`U+000A`) alone
/// (no additional CARRIAGE RETURN (`\r`/`U+000D`).
///
-/// Use the `format!` syntax to write data to the standard output.
-/// See `std::fmt` for more information.
+/// Use the [`format!`] syntax to write data to the standard output.
+/// See [`std::fmt`] for more information.
///
/// Use `println!` only for the primary output of your program. Use
-/// `eprintln!` instead to print error and progress messages.
+/// [`eprintln!`] instead to print error and progress messages.
///
+/// [`format!`]: ../std/macro.format.html
+/// [`std::fmt`]: ../std/fmt/index.html
+/// [`eprintln!`]: ..std/macro.eprint.html
/// # Panics
///
/// Panics if writing to `io::stdout` fails.
/// Macro for printing to the standard error.
///
-/// Equivalent to the `print!` macro, except that output goes to
-/// `io::stderr` instead of `io::stdout`. See `print!` for
+/// Equivalent to the [`print!`] macro, except that output goes to
+/// [`io::stderr`] instead of `io::stdout`. See [`print!`] for
/// example usage.
///
/// Use `eprint!` only for error and progress messages. Use `print!`
/// instead for the primary output of your program.
///
+/// [`io::stderr`]: ../std/io/struct.Stderr.html
+/// [`print!`]: ../std/macro.print.html
+///
/// # Panics
///
/// Panics if writing to `io::stderr` fails.
+///
+/// # Examples
+///
+/// ```
+/// eprint("Error: Could not complete task");
+/// ```
#[macro_export]
#[stable(feature = "eprint", since = "1.19.0")]
#[allow_internal_unstable]
/// Macro for printing to the standard error, with a newline.
///
-/// Equivalent to the `println!` macro, except that output goes to
-/// `io::stderr` instead of `io::stdout`. See `println!` for
+/// Equivalent to the [`println!`] macro, except that output goes to
+/// [`io::stderr`] instead of `io::stdout`. See [`println!`] for
/// example usage.
///
/// Use `eprintln!` only for error and progress messages. Use `println!`
/// instead for the primary output of your program.
///
+/// [`io::stderr`]: ../std/io/struct.Stderr.html
+/// [`println!`]: ../std/macro.println.html
+///
/// # Panics
///
/// Panics if writing to `io::stderr` fails.
+///
+/// # Examples
+///
+/// ```
+/// eprint("Error: Could not complete task");
+/// ```
#[macro_export]
#[stable(feature = "eprint", since = "1.19.0")]
macro_rules! eprintln {
/// The core macro for formatted string creation & output.
///
+ /// This macro functions by taking a formatting string literal containing
+ /// `{}` for each additional argument passed. `format_args!` prepares the
+ /// additional parameters to ensure the output can be interpreted as a string
+ /// and canonicalizes the arguments into a single type. Any value that implements
+ /// the [`Display`] trait can be passed to `format_args!`, as can any
+ /// [`Debug`] implementation be passed to a `{:?}` within the formatting string.
+ ///
/// This macro produces a value of type [`fmt::Arguments`]. This value can be
- /// passed to the functions in [`std::fmt`] for performing useful functions.
+ /// passed to the macros within [`std::fmt`] for performing useful redirection.
/// All other formatting macros ([`format!`], [`write!`], [`println!`], etc) are
- /// proxied through this one.
+ /// proxied through this one. `format_args!`, unlike its derived macros, avoids
+ /// heap allocations.
///
/// For more information, see the documentation in [`std::fmt`].
///
+ /// [`Display`]: ../std/fmt/trait.Display.html
+ /// [`Debug`]: ../std/fmt/trait.Debug.html
/// [`fmt::Arguments`]: ../std/fmt/struct.Arguments.html
/// [`std::fmt`]: ../std/fmt/index.html
/// [`format!`]: ../std/macro.format.html
/// compile time, yielding an expression of type `&'static str`.
///
/// If the environment variable is not defined, then a compilation error
- /// will be emitted. To not emit a compile error, use the `option_env!`
+ /// will be emitted. To not emit a compile error, use the [`option_env!`]
/// macro instead.
///
+ /// [`option_env!`]: ../std/macro.option_env.html
+ ///
/// # Examples
///
/// ```
/// If the named environment variable is present at compile time, this will
/// expand into an expression of type `Option<&'static str>` whose value is
/// `Some` of the value of the environment variable. If the environment
- /// variable is not present, then this will expand to `None`.
+ /// variable is not present, then this will expand to `None`. See
+ /// [`Option<T>`][option] for more information on this type.
///
/// A compile time error is never emitted when using this macro regardless
/// of whether the environment variable is present or not.
///
+ /// [option]: ../std/option/enum.Option.html
+ ///
/// # Examples
///
/// ```
/// A macro which expands to the line number on which it was invoked.
///
+ /// With [`column!`] and [`file!`], these macros provide debugging information for
+ /// developers about the location within the source.
+ ///
/// The expanded expression has type `u32`, and the returned line is not
/// the invocation of the `line!()` macro itself, but rather the first macro
/// invocation leading up to the invocation of the `line!()` macro.
///
+ /// [`column!`]: macro.column.html
+ /// [`file!`]: macro.file.html
+ ///
/// # Examples
///
/// ```
/// A macro which expands to the column number on which it was invoked.
///
+ /// With [`line!`] and [`file!`], these macros provide debugging information for
+ /// developers about the location within the source.
+ ///
/// The expanded expression has type `u32`, and the returned column is not
- /// the invocation of the `column!()` macro itself, but rather the first macro
- /// invocation leading up to the invocation of the `column!()` macro.
+ /// the invocation of the `column!` macro itself, but rather the first macro
+ /// invocation leading up to the invocation of the `column!` macro.
+ ///
+ /// [`line!`]: macro.line.html
+ /// [`file!`]: macro.file.html
///
/// # Examples
///
/// A macro which expands to the file name from which it was invoked.
///
+ /// With [`line!`] and [`column!`], these macros provide debugging information for
+ /// developers about the location within the source.
+ ///
+ ///
/// The expanded expression has type `&'static str`, and the returned file
- /// is not the invocation of the `file!()` macro itself, but rather the
- /// first macro invocation leading up to the invocation of the `file!()`
+ /// is not the invocation of the `file!` macro itself, but rather the
+ /// first macro invocation leading up to the invocation of the `file!`
/// macro.
///
+ /// [`line!`]: macro.line.html
+ /// [`column!`]: macro.column.html
+ ///
/// # Examples
///
/// ```
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