Trả về hàm

make_multiplier <- function(n) {
  function(x) x * n
}
triple <- make_multiplier(3)
print(triple(5))
print(make_multiplier(10)(5))

[1] 15
[1] 50

make_greeter <- function(greeting) {
  function(name) paste0(greeting, ", ", name, "!")
}
hello <- make_greeter("Hello")
hola <- make_greeter("Hola")
print(hello("Ada"))
print(hola("Ada"))

[1] "Hello, Ada!"
[1] "Hola, Ada!"

make_converter <- function(factor, offset = 0) {
  function(x) x * factor + offset
}
c_to_f <- make_converter(1.8, 32)
km_to_miles <- make_converter(0.621)
print(c_to_f(100))
print(km_to_miles(10))

[1] 212
[1] 6.21

compose <- function(f, g) function(x) g(f(x))
clean <- compose(trimws, toupper)
print(clean("  hi there "))

[1] "HI THERE"