[Haskell-cafe] Re: Why does Haskell have the if-then-else syntax?

Sebastian Sylvan sylvan at student.chalmers.se
Thu Jul 27 00:21:17 EDT 2006

On 7/27/06, Dan Doel <dan.doel at gmail.com> wrote:
> On 7/26/06, Donn Cave <donn at drizzle.com> wrote:
> > That looks to me like a different way to spell if then else, but maybe
> > that's the answer to the question - conceptually, for every "then" there
> > really is an "else", however you spell it, and only in a procedural language
> > does it make any sense to leave it implicit.  The exception that proves the
> > rule is "else return ()" -, e.g.,
> ...
> > Strictly speaking that generalizes to any functional context where a generic
> > value can be assigned to the else clause, but there don't tend to be that
> > many other such contexts.  Does that answer the question?
> I believe his question was why if-then-else is syntax, rather than the
> function he gave. Since haskell is non-strict, it doesn't need to be
> implemented as syntax (unlike, say, scheme, where it needs to be a
> special form/macro to avoid executing both branches).
> I imagine the answer is that having the syntax for it looks nicer/is
> clearer. "if a b c" could be more cryptic than "if a then b else c"
> for some values of a, b and c.

Also, you get less parenthesis:

myAbs x  = if x < 0 then negate x else x

Sebastian Sylvan
UIN: 44640862

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