Nobody can agree on the definition of a functional language. AFAIK, so-called "functional" languages like F# or O-Camel allow arbitrary side effects, unlike Haskell.
That's why you'd call Haskell a 'purely functional' language.
Re:Elm at Prezi
by 0xdeadbeefbabe on Thursday May 30, 2013 @04:37PM
(#5795056)
Any function changes the state of your machine, and you have to pretend your computer doesn't have memory or registers in order for this pure function side effect free stuff to make sense. When you said "know 100%" my ability to accept abstractions like that turned off.
IMO, that has nothing to do with it. Especially because you often do know 100% that this function has no side-effects.
It's because with Haskell you find a ton of errors at compile time and Clojure finds most issues at runtime.
Re:Elm at Prezi
by 0xdeadbeefbabe on Wednesday May 29, 2013 @04:57PM
(#5789032)
bah side effects what useful thing can you do without side effects? The only way to have no side effects is to frame the problem in a certain way.
Static typing can do a lot of good, but the stricter semantics of Haskell also goes a long way into writing code with fewer bugs.