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Open parenthesis, (, and open brace, {, are .Primitive functions in R.
(
{
.Primitive
Effectively, ( is semantically equivalent to the identity function(x) x, whereas { is slightly more interesting, see examples.
function(x) x
( \dots ){ \dots }
( \dots )
{ \dots }
For (, the result of evaluating the argument. This has visibility set, so will auto-print if used at top-level.
For {, the result of the last expression evaluated. This has the visibility of the last evaluation.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
if, return, etc for other objects used in the R language itself.
if
return
Syntax for operator precedence.
Syntax
f <- get("(") e <- expression(3 + 2 * 4) identical(f(e), e) do <- get("\{") do(x <- 3, y <- 2*x-3, 6-x-y); x; y ## note the differences (2+3) {2+3; 4+5} (invisible(2+3)) {invisible(2+3)}
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