myProgram : '{IO, Exception} ()
myProgram = '(printLine "Hello World")

myProgramWithArgs : '{IO, Exception} ()
myProgramWithArgs = 'let
  printLine ("Hello " ++ Optional.getOrElse "World" (List.head !getArgs) ++ "!")
.> run myProgram
.> run myProgramWithArgs Rebecca

Theruncommand is used to evaluate terms that require the IO ability within ucm. A program that performs IO cannot be evaluated in a watch expression but can be executed withrun.

Run takes a delayed computation and performs!myProgram,wheremyProgramis searched for in the most recent typechecked file, or in the codebase. The function provided to theruncommand must have a final return type of unit,(),and may perform the IO andExceptionabilities.

Any arguments following theruncommand will be passed as program arguments.