Package 'sloop'

Determine function type.

Description

This function figures out whether the input function is a regular/primitive/internal function, a internal/S3/S4 generic, or a S3/S4/RC method. This is function is slightly simplified as it's possible for a method from one class to be a generic for another class, but that seems like such a bad idea that hopefully no one has done it.

Usage

ftype(f)

Arguments

f	unquoted function name

Value

a character of vector of length 1 or 2.

Examples

ftype(`%in%`)
ftype(sum)
ftype(t.data.frame)
ftype(t.test) # Tricky!
ftype(writeLines)
ftype(unlist)

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Determine if a function is an S3 generic or S3 method.

Description

is_s3_generic() compares name checks for both internal and regular generics. is_s3_method() builds names of all possible generics for that function and then checks if any of them actually is a generic.

Usage

is_s3_generic(fname, env = parent.frame())

is_s3_method(fname, env = parent.frame())

Arguments

fname	Name of function as a string. Need name of function because it's impossible to determine whether or not a function is a S3 method based only on its contents.
env	Environment to search in.

Examples

is_s3_generic("mean")
is_s3_generic("sum")
is_s3_generic("[[")
is_s3_generic("unlist")
is_s3_generic("runif")

is_s3_method("t.data.frame")
is_s3_method("t.test") # Just tricking!
is_s3_method("as.data.frame")
is_s3_method("mean.Date")

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Determine the type of an object

Description

Tells you if you're dealing with an base, S3, S4, RC, or R6 object.

Usage

otype(x)

Arguments

x

An object

Examples

otype(1:10)
otype(mtcars)

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Compute the S3 class of an object

Description

Compared to class(), this always returns the class vector that is used for dispatch. This is most important for objects where the class attribute has not been set.

Usage

s3_class(x)

Arguments

x	A primitive type

Examples

s3_class(NULL)

s3_class(logical())
s3_class(integer())
s3_class(numeric())
s3_class(character())

s3_class(matrix())
s3_class(matrix(1))

s3_class(array())
s3_class(array(1))

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Illustrate S3 dispatch

Description

s3_dispatch() prints a list of all possible function names that will be considered for method dispatch. There are four possible states:

• ⁠=>⁠ method exists and is found by UseMethod().

• ⁠->⁠ method exists and is used by NextMethod().

• * method exists but is not used.

• Nothing (and greyed out in console): method does not exist.

Learn more at https://adv-r.hadley.nz/s3.html.

Usage

s3_dispatch(call, env = parent.frame())

Arguments

call	Example call to S3 method
env	Environment in which to evaluate call

Examples

x <- Sys.time()
s3_dispatch(print(x))
s3_dispatch(is.numeric(x))
s3_dispatch(as.Date(x))
s3_dispatch(sum(x))

# Internal vs. regular generic
x1 <- 1
x2 <- structure(2, class = "double")

my_length <- function(x) UseMethod("my_length")
s3_dispatch(my_length(x1))
s3_dispatch(my_length(x2))

length.double <- function(x) 10
s3_dispatch(length(x1))
s3_dispatch(length(x2))

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Find S3 method from its name

Description

Find S3 method from its name

Usage

s3_get_method(name)

Arguments

name	A string or unquoted symbol

Value

A function, or an error stating why the method could not be found

Examples

s3_get_method(mean.Date)
s3_get_method(weighted.mean.Date)

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List methods for a S3 or S4 generic (or class)

Description

Returns information about all methods belong to a generic or a class. In S3 and S4, methods belong to a generic, but it is often useful to see what generics have been provided methods for a given class. These are wrappers around utils::methods(), which returns a lot of useful information in an attribute.

Usage

s3_methods_class(x)

s3_methods_generic(x)

s4_methods_class(x)

s4_methods_generic(x)

Arguments

x	Name of class or generic

Value

A tibble with columns generic, visible, class, visible, and source.

Examples

s3_methods_class("Date")
s3_methods_generic("anova")

s4_methods_class("Date")
s4_methods_generic("anova")

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