Tuple and tuple indexing expressions
Tuple expressions
Syntax
TupleExpression :
(
InnerAttribute* TupleElements?)
TupleElements :
( Expression,
)+ Expression?
Tuples are written by enclosing zero or more comma-separated expressions in parentheses. They are used to create tuple-typed values.
# #![allow(unused_variables)] #fn main() { (0.0, 4.5); ("a", 4usize, true); (); #}
You can disambiguate a single-element tuple from a value in parentheses with a comma:
# #![allow(unused_variables)] #fn main() { (0,); // single-element tuple (0); // zero in parentheses #}
Tuple expression attributes
Inner attributes are allowed directly after the opening parenthesis of a tuple expression in the same expression contexts as attributes on block expressions.
Tuple indexing expressions
Syntax
TupleIndexingExpression :
Expression.
TUPLE_INDEX
Tuples and struct tuples can be indexed using the number corresponding to the position of the field. The index must be written as a decimal literal with no underscores or suffix. Tuple indexing expressions also differ from field expressions in that they can unambiguously be called as a function. In all other aspects they have the same behavior.
# #![allow(unused_variables)] #fn main() { # struct Point(f32, f32); let pair = (1, 2); assert_eq!(pair.1, 2); let unit_x = Point(1.0, 0.0); assert_eq!(unit_x.0, 1.0); #}