For symmetry, add functions array:scan-left and array:scan-right

[michaelhkay]

The fold-left and fold-right functions are defined both for sequences and arrays; symmetry demands that the same should apply to scan-left and scan-right.

[ChristianGruen]

Yes, we should do so. My favorite solution would be to offer the array functions for structured operations and the sequence functions for sequence operations, similar to what does array:for-each and fn:for-each (when you use the sequence functions, you can always create structured results if you need to).