diff options
Diffstat (limited to 'tests/untried/pos/t0031.scala')
-rw-r--r-- | tests/untried/pos/t0031.scala | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/tests/untried/pos/t0031.scala b/tests/untried/pos/t0031.scala new file mode 100644 index 000000000..d4050c818 --- /dev/null +++ b/tests/untried/pos/t0031.scala @@ -0,0 +1,29 @@ +object Main { + + trait Ensure[a] { + def ensure(postcondition: a => Boolean): a + } + + def require[a](precondition: => Boolean)(command: => a): Ensure[a] = + if (precondition) + new Ensure[a] { + def ensure(postcondition: a => Boolean): a = { + val result = command; + if (postcondition(result)) result + else sys.error("Assertion error") + } + } + else + sys.error("Assertion error"); + + def arb[a](s: List[a]) = + require (! s.isEmpty) { + s.head + } ensure (result => s contains result); + + def main(args: Array[String]) = { + val s = List(1, 2); + Console.println(arb(s)) + } + +} |