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rfunctionsymbolsequality

triple equal sign R

I am trying to create a function that checks for strict equality and I would like to use the triple equal sign. Some context:

> 3 == '3'
[1] TRUE
> FALSE == 0
[1] TRUE

All of the above check returns TRUE because the inputs are coerced to a common type. However I want to check for strict equality. The identical function does exactly what I need.

> identical(3,'3')
[1] FALSE
> identical(FALSE, 0)
[1] FALSE

Now I want to implement this in a more concise and less verbose way. As in Javascript I would like to use the triple equal sign. I wrote this function:

`===` <- function(a,b){
  identical(a,b)
}

However this doesn't behave as expected:

> 3 === 3
Error: unexpected '=' in "3 ==="

What am I missing? Thank you

Solution

  • You can define an infix operator (with the e in %e% for "equal";-):

    `%e%` <- function(a, b) identical(a, b)
3 %e% 3
#[1] TRUE

    Or if you want the triple-equal sign as

    `%===%` <- function(a, b) identical(a, b)
3 %===% 3
#[1] TRUE

    Or an example with vectors

    1:3 %===% 1:3
#[1] TRUE

    These infix operations (where the operator is used between the operands) can also be written as

    `%===%`(1:3, 1:3)

    in the same way that you can write

    `==`(3, 3)