unexpected IFS behavior with the newline character

[Darik Horn <dajhorn@vanadac.com>]

Can anybody explain this shell behavior?  -- It doesn't seem consistent 
with the documentation about how whitespace is interpreted as an 
internal field separator.

# IFS="\n"
# FOO="alpha\nbravo\ncharlie"
# for i in $FOO; do echo "%${i}%"; done
%alpha%
%%
%bravo%
%%
%charlie%

When ash or bash does the word splitting, a empty field is expanded. 
This behavior seems to happen only with the newline character.

# IFS="\n"
# FOO="alpha\n\n\nbravo\n\ncharlie"
# for i in $FOO; do echo "%${i}%"; done
%alpha%
%%
%%
%%
%%
%%
%bravo%
%%
%%
%%
%charlie%

In this case, the newline characters are not folded together like 
whitespace.  Generally, there are '2n-1' null expansions for each 'n' 
instances of the newline character in the input word.

TIA.