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bquote Partial substitution in expressions

Description

An analogue of the LISP backquote macro. bquote quotes its argument except that terms wrapped in .() are evaluated in the specified where environment. If splice = TRUE then terms wrapped in ..() are evaluated and spliced into a call.

Usage

bquote(expr, where = parent.frame(), splice = FALSE)

Arguments

expr	A language object.
where	An environment.
splice	Logical; if TRUE splicing is enabled.

Value

A language object.

See Also

quote, substitute

Examples

require(graphics)

a <- 2

bquote(a == a)
quote(a == a)

bquote(a == .(a))
substitute(a == A, list(A = a))

plot(1:10, a*(1:10), main = bquote(a == .(a)))

## to set a function default arg
default <- 1
bquote( function(x, y = .(default)) x+y )

exprs <- expression(x <- 1, y <- 2, x + y)
bquote(function() {..(exprs)}, splice = TRUE)