Conditionals

This page presents the computation operators that allow a choice depending on some condition. All possible returned values must be of the same type.

IF-ELSE

(if_else [BOOL] [C0 = COMPUTATION] [C1 = COMPUTATION])

Returns C0 is [BOOL] yields true, C1 otherwise.

COND

(cond
   ([B0 = BOOL] [C0 = COMPUTATION])
   ...
   ([BN = BOOL] [CN = COMPUTATION])
)

Returns [CI], such that [BI] is the first to hold true. If there is not such Bi, returns [CN].

SWITCH

(switch [T = COMPUTATION]
   ([V0 = COMPUTATION] [C0 = COMPUTATION])
   ...
   ([VN = BOOL] [CN = COMPUTATION])
   [D = COMPUTATION]
)
a

Returns the first CI such that VI is equal to T. If there is not such VI, returns [D].

Examples

(cond
   ((false) (false))
   ((false) (false))
   ((true)
      (cond
         ((false) (false))
         ((true) (not (is_member 3 test_list)))
         ((true) (false))
      )
   )
)

(switch 3
   (0 (false))
   (1 (false))
   (3 (true))
   (2 (false))
   (false)
)

(if_else (true)
   (if_else (false)
      (assert (false) FAILED: instruction ifelse E)
      (set test_var (true))
   )
   (assert (false) FAILED: instruction ifelse F)
)