Wolfram: Which, Switch

By Xah Lee. Date: 2022-07-02. Last updated: 2024-12-06.

Branch Switch by Testing Each Expression

Which[ test1, value1, test2, value2 etc]

eval each of the test in turn, return the value corresponding to the first one that yields True.

To have a catch-all test, add a last test to be just True.

Which[
3 > 9, aa,
3 > 4, bb,
True, cc
]

(* cc *)

Switch[test, pattern1, value1, pattern2, value2 etc]

eval test, then compares it with each of the pattern in turn, eval and return the value corresponding to the first match found.

The comparison is done with MatchQ[test, pattern] 〔see Wolfram: Pattern Matching〕

To have a catch-all test, add a last test to be the pattern _.

Switch[ 4,
3, aa,
4, bb,
_, cc
]

(* bb *)

Switch[ {x, y},
3, aa,
{_,_} , bb,
_, cc
]

(* bb *)