Question

I have a question which is an extension of another question.

I am wanting to be able to pipeline anonymous functions. In the previous question the answer to pipeline defined functions was to create a pipeline operator “%|>%” and to define it this way:

"%|>%" <- function(fun1, fun2){
              function(x){fun2(fun1(x))}
}

This would allow you to call a series of functions while continually passing the result of the previous function to the next. The caveat was that the functions to to be predefined. Now I’m trying to figure how to do this with anonymous functions. The previous solution which used predefined functions looks like this:

square <- function(x){x^2}
add5 <- function(x){x + 5}

pipelineTest <-
  square %|>%
  add5

Which gives you this behviour:

> pipelineTest(1:10)
 [1]   6   9  14  21  30  41  54  69  86 105

I would like to be able to define the pipelineTest function with anonymous functions like this:

anonymousPipelineTest <-
  function(x){x^2} %|>%
  function(x){x+5} %|>%
  x

When I try to call this with the same arguments as above I get the following:

> anonymousPipelineTest(1:10)
function(x){fun2(fun1(x))}
<environment: 0x000000000ba1c468>

What I’m hoping to get is the same result as pipelineTest(1:10). I know that this is a trivial example. What I’m really trying to get at is a way to pipeline anonymous functions. Thanks for the help!

Answer 1

Using Compose, and calling the resulting function gives this:

"%|>%" <- function(...) Compose(...)()

Now get rid of the ‘x’ as the final “function” (replaced with an actual function, that is not needed but here for example):

anonymousPipelineTest <-
     function(x){x^2} %|>%
     function(x){x+5} %|>% function(x){x}
anonymousPipelineTest(1:10)

[1]   6   9  14  21  30  41  54  69  86 105