10.5 Fundamentals - Forcing

• Lazy evaluation means arguments only evaluated when used
• “[can] lead to a real head-scratcher of a bug”

x <- 2
square <- power1(x)
x <- 3
square(4)
#> [1] 64

• Only applies if passing object as argument
• Here argument 2 evaluated when function called

square <- power1(2)
x <- 3
square(4)
#> [1] 16

So use force()! (Unless you want it to change with the x in the parent environment)