Syntax sugar: if type () -> X (nullary function returning X) is expected and we have an expression of type X, convert the expression into a lambda: () -> expr This allows custom functions to implement control structures like if-then-else, where the branches are evaluated only if needed

IfThenElse.ops

operators IfThenElse

group ifthenelse = "If…Then…Else…"

ifthenelse -> arithmetic, relations, brackets

test-custom-if-then-else.sl

extern puts(s: Byte *): Unit

extending Boolean {
  def `If…Then…Else…`(thenB: () -> (), elseB: () -> ()) =
    if this then thenB() else elseB()

  def &&(that: () -> Boolean) = if this then that() else false
  def ||(that: () -> Boolean) = if ¬this then that() else true
}

def main() = {
               // lambdaize!     lambdaize!
  If true Then puts("Then") Else puts("Else");
  if false && { puts("Word"); true } then puts("Word") // doesn't print anything
}