wrapr (version 1.9.6)

unpack: Unpack or bind values by names into the calling environment.

Description

Unpacks or binds values into the calling environment. Uses bquote escaping. NULL is a special case that is unpacked to all targets. NA targets are skipped. All non-NA target names must be unique.

Usage

unpack(wrapr_private_value, ...)

Arguments

wrapr_private_value

list of values to copy

...

argument names to write to

Value

value passed in (invisible)

Details

Note: a reference to the unpacker object is written into the unpacking environment as a side-effect of the implied array assignment. Array-assign form can not use the names: ., wrapr_private_self, value, or unpack. Function form can not use the names: . or wrapr_private_value. For more details please see here http://www.win-vector.com/blog/2020/01/unpack-your-values-in-r/.

Related work includes Python tuple unpacking, zeallot's arrow, and vadr::bind.

Examples

# NOT RUN {
# named unpacking
# looks like assignment: DESTINATION = NAME_VALUE_USING
d <- data.frame(x = 1:2,
                g=c('test', 'train'),
                stringsAsFactors = FALSE)
unpack[train_set = train, test_set = test] <- split(d, d$g)
# train_set and test_set now correctly split
print(train_set)
print(test_set)
rm(list = c('train_set', 'test_set'))

# named unpacking NEWNAME = OLDNAME implicit form
# values are matched by name, not index
unpack[train, test] <- split(d, d$g)
print(train)
print(test)
rm(list = c('train', 'test'))

# function version
unpack(split(d, d$g), train, test)
print(train)
print(test)
rm(list = c('train', 'test'))

# pipe version
split(d, d$g) %.>% unpack(., train, test)
print(train)
print(test)
rm(list = c('train', 'test'))
# Note: above is wrapr dot-pipe, piping does not currently work with
# magrittr pipe due to magrittr's introduction of temporary
# intermediate environments during evaluation.

# }