Reverse a String without using reverse function

Question

I'm unable to find where the mistake is in below code Reverse a string without reverse function: a!localVariables(
 local!result: ri!result,
 local!index: if(
 a!isNullOrEmpty(ri!index),
 length(ri!Input),
 ri!index
 ),
 if(
 ri!index < 1,
 ri!result,
 rule!T_Reversestring(
 ri!Input,
 local!index - 1,
 concat(
 local!result,
 index(ri!Input, local!index)
 )
 )
 )

Stefan Helzle · Accepted Answer

No recursion required 
 ri!text[len(ri!text) - enumerate(len(ri!text))]

Mike Schmitt · Answer

Stefan's elegant tiny answer got me thinking about what the "elegant but somewhat more verbose" answer might be. Once again we can rely on a!forEach() and the dataSubset sort. The advantage with this approach is it could potentially handle use cases with a little more nuance if needed. 
 a!localVariables(
 local!sortMap: a!forEach(
 enumerate(len(ri!text))+1,
 
 a!map(
 index: fv!item,
 currentLetter: ri!text[fv!item]
 )
 ),
 
 local!sortedSet: todatasubset(
 arrayToPage: local!sortMap,
 pagingConfiguration: a!pagingInfo(1, -1, a!sortInfo(field: "index", ascending: false()))
 ).data,
 
 concat(local!sortedSet.currentLetter)
)

Reverse a String without using reverse function

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