A loop is based on a conditional jump (aka. a flow control statement in imperative langs) which makes all the difference. The problem with jumps (is usually called a jump, purely arbitrary jump) is that they are arbitrary: http://news.ycombinator.com/item?id=4627730

How do know what happens at an end-brace? Have to go look at the matching start-brace to see if it is a while or for or if. Madness! Can I assume the code above even executed once? No! What of I check the guard clause first? It has variables! Oh heavens, control flow depends on arbitrary RUNTIME data!?