Problem with ?Syntax
I wasn't claiming there was an ambiguity but it does not perform according to the operator precedence documented in ?Syntax . If it performed as documented it would give an error. On Sat, Feb 20, 2010 at 6:57 AM, Barry Rowlingson
<b.rowlingson at lancaster.ac.uk> wrote:
On Sat, Feb 20, 2010 at 9:52 AM, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
In ?Syntax [ is given as higher priority than $ but BOD$demand[3] seems to be the same as (BOD$demand)[3] contrary to [ being higher priority.
BOD$demand[3]
[1] 19
(BOD$demand)[3]
[1] 19 What is the rule being used here?
?I think its the parser rule that defines the syntax of $ on a list. Does: ?BOD$(demand[3]) even work?
BOD$(demand[3])
Error: unexpected '(' in "BOD$("
?- no. The parser sees a $ and then gets the next token (gram.y shows
this to be a symbol or a string constant) as the thing to deal with.
Symbols ?I can't think of an example where $ and [ could have
ambiguous precedence that is syntactically correct, so maybe the order
is irrelevant...
?Just for fun:
x=list(a=1,b=2) x$"a[1]"=2 x$"a[1]"
[1] 2
x$a[1]
[1] 1 Barry