ExpressionBuilder b = new ExpressionBuilder();
Expression e;
// function
assertEquals(ff.function("pi"), b.function().name("pi").build());
assertEquals(ff.function("abs", ff.literal(-2)), b.function().name("abs").param().literal(-2).build());
assertEquals(ff.function("abs", ff.literal(-2)), b.function("abs").param().literal(-2).build());
assertEquals(ff.function("min", ff.literal(1), ff.literal(2)),
b.function("min").param().literal(1).param().literal(2).build());