Just An Application

July 3, 2014

So Swift Then: Tuples – One More Thing

A tuple value is an example of a parenthesized expression the syntax for which is as follows

    parenthesized-expression : '(' expression-element-list? ')'
    
    expression-element-list : expression-element
                            | expression-element ',' expression-element-list
                            
    expression-element      : expression
                            | identifier ':' expression

In the case of a tuple value, if the expression-element is always an expression you get an ordinary tuple,

    ("cod", "dab", "eel")

if the expression-element is always an identifier a colon and an expression you get a tuple with named values,

    (first:"cod", second:"dab", third:"eel")

but the syntax at least does not preclude having a mixture of both.

This would seem to imply that you should be able to do something like this

    let mixedTuple = (first:"cod", "dab", third:"eel")

and interestingly enough a little experimentation reveals that you can do exactly that.

At the moment I can’t think why you might want to do this but if you can think of a reason then currently at least you will be able to.


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