Add the reverseRangeFunc & rangeFunc methods on ArrayUtils contract to support decreasing ranges

[m-Peter]

Examples:

var range = ArrayUtils.range(0, 10)
range == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

range = ArrayUtils.reverseRange(10, 0)
range == [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]

Update: Cadence tests for the ArrayUtils smart contract, were added:

flow test --cover test/*.cdc

Test results: "test/ArrayUtils_test.cdc"
- PASS: testRange
- PASS: testTransform
- PASS: testIterate
- PASS: testMap
- PASS: testMapStrings
- PASS: testReduce
Coverage: 100.0% of statements

[m-Peter]

cc @bjartek @bjartek @austinkline @turbolent
I have added the first unit test for ArrayUtils smart contract, using the Cadence Testing Framework 🙏
Let me know your thoughts!

[austinkline]

@bluesign thoughts on this? We might be better off defining a reverseRangeFunc so that users know this is an option. I would expect that end being less than start would panic but totally get the value of combining these.

[m-Peter]

I have added separate methods for reverseRangeFunc and reverseRange, to be more explicit 🙏

[m-Peter]

@austinkline Kind reminder 🙏

[austinkline]

@austinkline Kind reminder 🙏

Thank you!

[austinkline]

This LGTM but @bluesign @bjartek any other concerns or comments?

[bjartek]

LGTM

[bluesign]

LGTM

[turbolent]

BTW, seeing the range helper functions in the array utils contract triggered this feature idea for the Cadence standard library: onflow/cadence#2482. Please chime in if you would like to see range functionality in Cadence itself!

[m-Peter]

That's nice! I'll add some feedback there too 🙏