Side effects

Even if the functional programming style prefers writing pure functions without side-effects, sometimes side-effects are the reason for running the function in the first place.

This section lists the most important functions with side-effects that are defined in the SCL standard library.

Printing

print :: Show a => a -> <Proc> () (Prelude)

Prints the given value in the console.

printString :: String -> <Proc> () (Prelude)

Prints the given string to the console.

printError :: String -> <Proc> () (Prelude)

Prints an error message to the console.

printingToFile :: String -> <b> a -> <b> a (Prelude)

printingToFile "fileName" expression executes the expression so that all its console prints are written to the file given as a first parameter. The file will be written with UTF-8 encoding.

References

ref :: a -> <Proc> Ref a (Prelude)

Creates a new reference with the given initial value.

getRef :: Ref a -> <Proc> a (Prelude)

Returns the current value of the reference.

(:=) :: Ref a -> a -> <Proc> () (Prelude)

Sets a new value for the reference.

Mutable arrays

data T a (ArrayList)

Type of lists.

new :: () -> <Proc> ArrayList.T a (ArrayList)

Constructs a new list.

add :: ArrayList.T a -> a -> <Proc> () (ArrayList)

Adds an element to the list.

remove :: ArrayList.T a -> Integer -> <Proc> a (ArrayList)

Removes the i:th element of the list

get :: ArrayList.T a -> Integer -> <Proc> a (ArrayList)

Gets the i:th element of the list.

length :: ArrayList.T a -> <Proc> Integer (ArrayList)

The current length of the list.

contains :: ArrayList.T a -> a -> <Proc> Boolean (ArrayList)
iter :: (a -> <b> ()) -> ArrayList.T a -> <Proc,b> () (ArrayList)

Iterates thru the list. The elements added during the iteration are also iterated.

for :: ArrayList.T a -> (a -> <b> ()) -> <Proc,b> () (ArrayList)

'iter' with swapped parameter.

mapInPlace :: (a -> <b> a) -> ArrayList.T a -> <Proc,b> ArrayList.T a (ArrayList)

Replaces every element of the list by the result of applying the element to the given function.

popUntilEmpty :: ArrayList.T a -> (a -> <b> ()) -> <Proc,b> () (ArrayList)

Pops the last element of the list until list becomes empty.

Escaping side-effects

runProc :: <Proc,b> a -> <b> a (Builtin)