reduce unbound within \context lambda

[Aaron Hill]

I encountered an unexpected error where reduce is unbound when 
specifying a lambda within a \context block:

%%%%
\version "2.19.82"
\layout { \context { \Voice
  \override NoteHead.color = #(lambda (grob)
    (display (reduce + 0 '(1 2 3 4))) red)
} }
{ b'4 }
%%%%

Compare to the following snippets that work:

%%%%
\version "2.19.82"
{ \override NoteHead.color = #(lambda (grob)
    (display (reduce + 0 '(1 2 3 4))) red)
  b'4 }
%%%%
\version "2.19.82"
#(define (foo grob)
  (display (reduce + 0 '(1 2 3 4))) red)
\layout { \context { \Voice
  \override NoteHead.color = #foo
} }
{ b'4 }
%%%%

fold is also unbound, although map works fine.

Am I missing a subtlety here, or is this a bug?


-- Aaron Hill