Create new function that supports 'quasi-quosure' syntax
Usage
new_function2(
args = alist(),
body = {
},
env = parent.frame(),
quote_type = c("unquoted", "quote", "quo"),
quasi_env = parent.frame()
)
Arguments
- args
named list of function formals
- body
function body expression, supports 'quasi-quosure' syntax
- env
declare environment of the function
- quote_type
character, whether
body
is unquoted, quoted, or a 'quo' object (from 'rlang' package)- quasi_env
where the 'quasi-quosure' should be evaluated, default is parent environment
Details
An unquoted body expression will be quoted, all the
expressions with 'quasi-quosure' like !!var
will be evaluated
and substituted with the value of var
. For a 'quosure',
quo_squash
will be applied. A quoted
expression will not be substitute, but will be expanded if any
'quasi-quosure' detected
args
must be a list
object, see formals
.
For arguments with no default values, or quoted defaults, use
alist
. An arg=alist(a=)
will result in a
function like function(a){...}
. See examples for more details.
Examples
# ------------ standard usage ------------
x <- 1:10
f1 <- new_function2(alist(a=), { print(a + x) }, env = environment())
f1(0)
#> [1] 1 2 3 4 5 6 7 8 9 10
x <- 20:23
f1(0) # result changed as x changed
#> [1] 20 21 22 23
# ------------ 'quasi-quosure' syntax ------------
x <- 1:10
f2 <- new_function2(alist(a=), { print(a + !!x) })
print(f2)
#> function (a)
#> {
#> print(a + 1:10)
#> }
#> <environment: 0x56521abf6778>
f2(0)
#> [1] 1 2 3 4 5 6 7 8 9 10
x <- 20:23
f2(0) # result doesn't change as f2 doesn't depend on x anymore
#> [1] 1 2 3 4 5 6 7 8 9 10
# ------------ argument settings ------------
default <- 123
# default with values pre-specified
new_function2(list(a = default)) # function (a = 123){}
#> function (a = 123)
#> {
#> }
#> <environment: 0x56521f3bc4f0>
# default with values unevaluated
new_function2(list(a = quote(default))) # function (a = default){}
#> function (a = default)
#> {
#> }
#> <environment: 0x565218a873c8>
new_function2(alist(a = default))
#> function (a = default)
#> {
#> }
#> <environment: 0x56521c027aa0>
# missing default
new_function2(alist(a = )) # function (a){}
#> function (a)
#> {
#> }
#> <environment: 0x56521ac92d80>