r - Why does switch("d", a = 1, b = 2) not give any warning, error, or output?

Question

Clearly, switch("d", a = 1, b = 2) does not have a default value, a value matching "d", or any reason to return anything. The documentation for switch tells us that "A warning is signaled if no alternatives are provided, as this is usually a coding error". However, when I run switch("d", a = 1, b = 2), nothing happens at all. I get no outputs, warnings, or errors. What have I misunderstood about R's switch? I expected a warning.

Answer 1

A call to switch() evaluates to NULL if none of the arguments get matched to the supplied value. If EXPR evaluates to a character you can specify a default value by including an unnamed argument. If EXPR evaluates to integer, numeric or logical you cannot specify a default for it. You can always use a different conditional operator if this is too limiting.