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assert

core-api



    macro
    boot.janet on line 147, column 1

    (assert x &opt err)

    Throw an error if x is not truthy. Will not evaluate `err` if x is 
    truthy.

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(assert :dude :what?) # => :dude

(assert :dude :dude) # => :dude

(assert ( $=$  :dude :what?) "Where's my car?")
# => error: Where's my car?
# =>  in _thunk [repl] (tailcall) on line 84, column 1

(assert ( $=$  :dude :dude) "Where's my car?") # => true

jgartePlayground

(var a 0)
(assert (pos? a) "A is definitely not positive")
# error: A is definitely not positive
#  in assert [boot.janet] on line 149, column 11
#  in _thunk [repl] (tailcall) on line 3, column 1

pepePlayground