Understanding when the && operator short circuits [duplicate]

StackOverflow https://stackoverflow.com/questions/16844418

  •  30-05-2022
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Question

Perhaps I'm missing something obvious.

In R, TRUE && NA evalues to NA. This doesn't make sense to me, because && should evaluate left to right, and stop as soon as one of its conditions is true.

Was it helpful?

Solution

This doesn't make sense to me, because && should evaluate left to right, and stop as soon as one of its conditions is true.

This is wrong. You are mixing up && with ||:

  • TRUE && FALSE gives FALSE
    • && requires both conditions to be TRUE
    • && will short-circuit on FALSE
  • TRUE || FALSE gives TRUE
    • || requires a single condition to be TRUE
    • || will short-circuit on TRUE

Also,

TRUE || NA

gives

TRUE
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