From @smls

The normal reduce meta-operator doesn't flatten anything​:

  ➜ say [,] <a b>, <c d>, <e f>;
  ((a b) (c d) (e f))

But the triangle-reduce operator flattens each of the intermediate
results it returns​:

  ➜ .say for [\,] <a b>, <c d>, <e f>;
  (a b)
  (a b c d)
  (a b c d e f)

The result I expected for that last statement, is​:

  ((a b))
  ((a b) (c d))
  ((a b) (c d) (e f))

From @FCO

rakudo/rakudo#1041

Em Sat, 21 Jan 2017 06​:23​:02 -0800, smls75@​gmail.com escreveu​:

The normal reduce meta-operator doesn't flatten anything​:

➜  say \[,\] \<a b>, \<c d>, \<e f>;
\(\(a b\) \(c d\) \(e f\)\)

But the triangle-reduce operator flattens each of the intermediate
results it returns​:

➜  \.say for \[\\,\] \<a b>, \<c d>, \<e f>;
\(a b\)
\(a b c d\)
\(a b c d e f\)

The result I expected for that last statement, is​:

\(\(a b\)\)
\(\(a b\) \(c d\)\)
\(\(a b\) \(c d\) \(e f\)\)

The RT System itself - Status changed from 'new' to 'open'

@FCO - Status changed from 'open' to 'resolved'

From @zoffixznet

Tests in​:
Raku/roast@61046c6
Raku/roast@c30eb54
Raku/roast@fa228b0