How do I write a function's code to a string?

Question

Suppose I have:

test <- function(x) x + 1
test
function(x)
  x + 1

I would like to somehow save the output produced by invoking test to a string (i.e. the function declaration) but can't think of a way to do it.

Is this after you declare the test. Something like deparse(test) — akrun
– akrun, Commented Jul 24, 2019 at 15:20

akrun · Accepted Answer · 2019-07-24 15:30:17Z

6

We can use deparse

paste(deparse(test), collapse = " ")
#[1] "function (x)  x + 1"

Also, if we need to extract the components of the function, use body

body(test)

Or split it to a list

as.list(test)

edited Jul 24, 2019 at 15:30

answered Jul 24, 2019 at 15:24

akrun

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Comments

Denis · Accepted Answer · 2019-07-24 18:30:35Z

6

You are looking for capture.output.

> z=paste(capture.output(test), collapse = " ")
> z
[1] "function(x) x + 1"

edited Jul 24, 2019 at 18:30

Denis

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answered Jul 24, 2019 at 15:20

boski

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3 Comments

Denis Over a year ago

This works but was hoping this was going to be the last-resort solution. Is there anything better other than capture.output? No other function to just dump the definition of a function?

Denis Over a year ago

Coming from other programming languages (.NET, Java, etc.), creators of libraries would always love to change their toString() method so it prints their object more succinctly or prettier, etc. Having your production app and its reputation depend on how an object is printed on the command-line by a third-party developer you have no access to is generally not an accepted practice in most languages I am familiar. R is new to me so maybe the rule breaks on this one.

Brian Over a year ago

@Denis, in R, sometimes complex objects (or more specifically, their classes) will have print.yourclass methods, but I've never seen that for a standalone function.

Ben Bolker · Accepted Answer · 2019-07-24 15:35:43Z

2

Another possibility?

dput(test,textConnection("test_txt",open="w"))

or the same with dump()

answered Jul 24, 2019 at 15:35

Ben Bolker

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