<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Got it. No doubt some of this figures into why I was beaten bloody by ghci last night. Is there a number "tree" somewhere that shows the heirarchy?<br><br>Michael<br><br>--- On <b>Mon, 10/26/09, Daniel Fischer <i><daniel.is.fischer@web.de></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Daniel Fischer <daniel.is.fischer@web.de><br>Subject: Re: [Haskell-cafe] Fortran mixed mode arithmetic expressions -> Haskell<br>To: "michael rice" <nowgate@yahoo.com>, haskell-cafe@haskell.org<br>Date: Monday, October 26, 2009, 1:09 PM<br><br><div class="plainMail">Am Monday 26 October 2009 17:24:46 schrieben Sie:<br>> Being new to Haskell, I take it (^) and (^^) would be the preferred<br>> exponential "operator." When (how,where,why) would one use (**)?<br><br>The beasts
have different types and are for different things:<br>Prelude> :i (^)<br>(^) :: (Num a, Integral b) => a -> b -> a -- Defined in GHC.Real<br>infixr 8 ^<br><br>This one raises any number to a nonnegative integral power.<br>A typical implementation would be power by repeated squaring.<br><br>Prelude> :i (^^)<br>(^^) :: (Fractional a, Integral b) => a -> b -> a<br> -- Defined in GHC.Real<br>infixr 8 ^^<br><br>This one allows also negative powers, so the type of base must allow inversion, hence it <br>must belong to Fractional. The exponent must still be an integer, you can't use this for <br>n-th roots or similar.<br>A typical implementation would be power by repeated squaring, followed by (1/) if the <br>exponent is negative.<br><br>Prelude> :i (**)<br>class (Fractional a) => Floating a where<br> ...<br> (**) :: a -> a -> a<br> ...<br>
-- Defined in GHC.Float<br>infixr 8 **<br><br>This one raises a floating point number to an arbitrary power, so you can use it for n-th <br>roots.<br>A typical implementation would be<br>b ** e = exp (e*log b).<br><br></div></blockquote></td></tr></table><br>