Hello Russel,
You're tripping over a syntactic wrinkle: a singleton tuple is written
with a curious concluding comma, as in
var onetuple = (1,);
Without it, the parentheses are taken just for grouping. E.g.,
var justaone = (1);
results in a variabe of type int, not 1*int.
In your example below, when the first two 5-tuples are commented out
there's only one left. So in order for testData to be a tuple containing
just the one 5-tuple, it needs the trailing comma:
const testData = ( ([0.0, 2.0, 2.0, 4.0], 2.0, 2.0, 1.0, sqrt(2.0)), );
Without it, the outer parens are used for normal grammatical grouping but
otherwise ignored. That leaves testData being the 5-tuple itself.
(Which, being non-homogeneous, can't be iterated over with a normal for
loop. I gather having that for loop iterate over the elements of the
5-tuple wasn't your intent anyway.)
--
Paul Cassella
On Sat, 3 Sep 2016, Russel Winder wrote:
> The code:
>
> const testData = (
> //([0.0, 2.0], 1.0, 1.0, 1.0, sqrt(2.0)),
> //([0.0, 2.0, 4.0], 2.0, 2.0, 1.0, sqrt(2.0)),
> ([0.0, 2.0, 2.0, 4.0], 2.0, 2.0, 1.0, sqrt(2.0))
> );
>
> proc main() {
> for item in testData {}
> }
>
>
> fails to compile with the message:
>
> test_statistics.chpl:7: In function 'main':
> test_statistics.chpl:8: error: Cannot iterate over non-homogeneous tuples. If
> you intended to use zippered iteration, add the new keyword 'zip' before the
> tuple of iteratable expressions.
>
>
> If the tuples that are commented are uncommented then the code compiles
> fine.
>
> ------------------------------------------------------------------------------
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