hostilefork
AI~ (Array/Initial) doesn't work with functions
Supplying ARRAY/INITIAL in Rebol with a function value initiates each element of the array with the product of a fresh invocation of the function. This doesn't happen in Rebmu. Rebol 3:
>> n: 1 array/initial 4 does [++ n]
== [1 2 3 4]
And in Rebmu:
>> rebmu/debug [I&[a+Jn]Aai~4 i]
Executing: [i: & [a+ j n] a: ai~ 4 i]
== [1 1 1 1]
Note that your example requires a get-word even in regular Rebol.
>> rebmu/debug [I&[a+Jn]Aai~4 :i]
Executing: [i: & [a+ j n] a: ai~ 4 :i]
== [1 2 3 4]
...however, it wasn't working even when passing in the result of the function generator. (which was presumably what you tried first). So yep, there was a bug.
Fixed with the assistance of a helpful person on StackOverflow :-)
http://stackoverflow.com/questions/22892499/
Ah, while it did fix the specific case of function values it changes the evaluation rules...so now you can't pass ordinary variables or expressions because of the quoting. It effectively makes AI~ have a different prototype which isn't what's needed... see comment on SO.