lua/examples/errors.carp at master · carpentry-org/lua · GitHub

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(load "https://github.com/carpentry-org/lua@0.2.0")

(Lua.setup "lua")

; demonstrating error handling across the API
(defn main []
  (Lua.with-lua-do
    (Lua.libs lua)

    (match (Luax.do-in lua "x = 1 + 1")
      (Result.Success _) (IO.println "valid code: ok")
      (Result.Error e) (IO.errorln &e))

    (match (Luax.do-in lua "x = nil + 1")
      (Result.Success _) (IO.println "should not reach here")
      (Result.Error e) (IO.println &(fmt "caught: %s" &e)))

    (match (Luax.call-fn lua no-such-function Lua.get-int)
      (Result.Success _) (IO.println "should not reach here")
      (Result.Error e) (IO.println &(fmt "caught: %s" &e)))

    (ignore (Lua.do-string lua (cstr "function boom() error('kaboom!') end")))
    (match (Luax.call-fn lua boom Lua.get-int)
      (Result.Success _) (IO.println "should not reach here")
      (Result.Error e) (IO.println &(fmt "caught: %s" &e)))

    (match (Lua.eval-file lua "nonexistent.lua")
      (Result.Success _) (IO.println "should not reach here")
      (Result.Error e) (IO.println &(fmt "caught: %s" &e)))

    (Lua.push-int lua 42)
    (match (Luax.maybe-get-string lua -1)
      (Maybe.Just _) (IO.println "should not reach here")
      (Maybe.Nothing) (IO.println "type mismatch: got Nothing (expected)"))
    (match (Luax.maybe-get-int lua -1)
      (Maybe.Just n) (IO.println &(fmt "correct type: %d" n))
      (Maybe.Nothing) (IO.println "should not reach here"))
    (Lua.pop lua 1)

    (Luax.set-int-global lua "present" 1)
    (IO.println &(fmt "present exists: %s" &(str (Lua.global-exists? lua "present"))))
    (IO.println &(fmt "absent exists: %s" &(str (Lua.global-exists? lua "absent"))))))