Range expressions

Syntax
RangeExpression :
      RangeExpr
   | RangeFromExpr
   | RangeToExpr
   | RangeFullExpr
   | RangeInclusiveExpr
   | RangeToInclusiveExpr

RangeExpr :
   Expression .. Expression

RangeFromExpr :
   Expression ..

RangeToExpr :
   .. Expression

RangeFullExpr :
   ..

RangeInclusiveExpr :
   Expression ..= Expression

RangeToInclusiveExpr :
   ..= Expression

The .. and ..= operators will construct an object of one of the std::ops::Range (or core::ops::Range) variants, according to the following table:

ProductionSyntaxTypeRange
RangeExprstart..endstd::ops::Rangestart ≤ x < end
RangeFromExprstart..std::ops::RangeFromstart ≤ x
RangeToExpr..endstd::ops::RangeTox < end
RangeFullExpr..std::ops::RangeFull-
RangeInclusiveExprstart..=endstd::ops::RangeInclusivestart ≤ x ≤ end
RangeToInclusiveExpr..=endstd::ops::RangeToInclusivex ≤ end

Examples:


#![allow(unused_variables)]
fn main() {
1..2;   // std::ops::Range
3..;    // std::ops::RangeFrom
..4;    // std::ops::RangeTo
..;     // std::ops::RangeFull
5..=6;  // std::ops::RangeInclusive
..=7;   // std::ops::RangeToInclusive
}

The following expressions are equivalent.


#![allow(unused_variables)]
fn main() {
let x = std::ops::Range {start: 0, end: 10};
let y = 0..10;

assert_eq!(x, y);
}

Ranges can be used in for loops:


#![allow(unused_variables)]
fn main() {
for i in 1..11 {
    println!("{}", i);
}
}