Tests if a function, provided by its name, can be transformed.

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.

can_loop_transform_body(fun_name, fun_body, fun, env)

can_loop_transform_(fun)

can_loop_transform(fun)

Arguments

fun_name	Name of the recursive function.
fun_body	The user-transformed function body.
fun	The function to check. Must be provided by its (bare symbol) name.
env	Environment used to look up variables used in fun_body.

Functions

• can_loop_transform_body: This version expects fun_body to be both tested and user-transformed.

• can_loop_transform_: This version expects fun to be quosure.

• can_loop_transform: This version quotes fun itself.

Examples

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
#> Warning: The function cannot be transformed since it contains a recursive call inside a call.
#> [1] FALSE
can_loop_transform(factorial_acc) # TRUE
#> [1] TRUE

can_loop_transform_(rlang::quo(factorial))     # FALSE -- and prints a warning
#> Warning: The function cannot be transformed since it contains a recursive call inside a call.
#> [1] FALSE
can_loop_transform_(rlang::quo(factorial_acc)) # TRUE
#> [1] TRUE