src/libcollections/macros.rs

   1 // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 /// Creates a `Vec` containing the arguments.
  12 ///
  13 /// `vec!` allows `Vec`s to be defined with the same syntax as array expressions.
  14 /// There are two forms of this macro:
  15 ///
  16 /// - Create a `Vec` containing a given list of elements:
  17 ///
  18 /// ```
  19 /// let v = vec![1, 2, 3];
  20 /// assert_eq!(v[0], 1);
  21 /// assert_eq!(v[1], 2);
  22 /// assert_eq!(v[2], 3);
  23 /// ```
  24 ///
  25 /// - Create a `Vec` from a given element and size:
  26 ///
  27 /// ```
  28 /// let v = vec![1; 3];
  29 /// assert_eq!(v, [1, 1, 1]);
  30 /// ```
  31 ///
  32 /// Note that unlike array expressions this syntax supports all elements
  33 /// which implement `Clone` and the number of elements doesn't have to be
  34 /// a constant.
  35 ///
  36 /// This will use `clone()` to duplicate an expression, so one should be careful
  37 /// using this with types having a nonstandard `Clone` implementation. For
  38 /// example, `vec![Rc::new(1); 5]` will create a vector of five references
  39 /// to the same boxed integer value, not five references pointing to independently
  40 /// boxed integers.
  41 #[cfg(not(test))]
  42 #[macro_export]
  43 #[stable(feature = "rust1", since = "1.0.0")]
  44 #[allow_internal_unstable]
  45 macro_rules! vec {
  46     ($elem:expr; $n:expr) => (
  47         $crate::vec::from_elem($elem, $n)
  48     );
  49     ($($x:expr),*) => (
  50         <[_]>::into_vec(box [$($x),*])
  51     );
  52     ($($x:expr,)*) => (vec![$($x),*])
  53 }
  54
  55 // HACK(japaric): with cfg(test) the inherent `[T]::into_vec` method, which is
  56 // required for this macro definition, is not available. Instead use the
  57 // `slice::into_vec`  function which is only available with cfg(test)
  58 // NB see the slice::hack module in slice.rs for more information
  59 #[cfg(test)]
  60 macro_rules! vec {
  61     ($elem:expr; $n:expr) => (
  62         $crate::vec::from_elem($elem, $n)
  63     );
  64     ($($x:expr),*) => (
  65         $crate::slice::into_vec(box [$($x),*])
  66     );
  67     ($($x:expr,)*) => (vec![$($x),*])
  68 }
  69
  70 /// Use the syntax described in `std::fmt` to create a value of type `String`.
  71 /// See `std::fmt` for more information.
  72 ///
  73 /// # Examples
  74 ///
  75 /// ```
  76 /// format!("test");
  77 /// format!("hello {}", "world!");
  78 /// format!("x = {}, y = {y}", 10, y = 30);
  79 /// ```
  80 #[macro_export]
  81 #[stable(feature = "rust1", since = "1.0.0")]
  82 macro_rules! format {
  83     ($($arg:tt)*) => ($crate::fmt::format(format_args!($($arg)*)))
  84 }