can_loop_transform: Tests if a function, provided by its name, can be...
In mailund/tailr: Automatic Tail Recursion Optimisation

Description Usage Arguments Functions Examples

This function analyses a recursive function to check if we can transform it into a loop or trampoline version with transform. Since this function needs to handle recursive functions, it needs to know the name of its input function, so this must be provided as a bare symbol.

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can_loop_transform_(fun)

can_loop_transform(fun)

fun

The function to check. Must be provided by its (bare symbol) name.

can_loop_transform_: This version expects fun to be quosure.
can_loop_transform: This version quotes fun itself.

factorial <- function(n)
    if (n <= 1) 1 else n * factorial(n - 1)
factorial_acc <- function(n, acc = 1)
    if (n <= 1) acc else factorial_acc(n - 1, n * acc)

can_loop_transform(factorial) # FALSE -- and prints a warning
can_loop_transform(factorial_acc) # TRUE

can_loop_transform_(rlang::quo(factorial)) # FALSE -- and prints a warning
can_loop_transform_(rlang::quo(factorial_acc)) # TRUE