Date: Mar 14, 2006 8:55 AM
Author: matt271829-news@yahoo.co.uk
Subject: Re: Reason for operator precedence

bri...@encompasserve.org wrote:

> In article <1142342196.542632.294210@i39g2000cwa.googlegroups.com>, matt271829-news@yahoo.co.uk writes:

> >

> > Tony wrote:

> >> Hi all.

> >>

> >> Hope this isn't a silly question.

> >>

> >> I was wondering what the reason is for having multiple levels of operator

> >> precedence?

> >>

> >> Phrased another way, why is it that we don't just evaluate everything from

> >> left to right?

> >>

> >> Having multiple levels of precedence obviously adds complexity, so I assume

> >> there must be some payback. However, I don't see what it is.

> >>

> >

> > As far as addition/subtraction vs multiplication/division is concerned,

> > one reason is to ensure that the distributive property of

> > multiplication works sensibly. For example, we want 3*(4 + 6) = 3*4 +

> > 3*6 = 3*(6 + 4) = 3*6 + 3*4.

>

> Remember that what we're talking about here is merely a notational

> convention. It has nothing whatsoever to do with the distributive

> property of multiplication over addition.

>

> You can express the distributive law for multiplication over division

> using parentheses:

>

> a*(b+c) = (a*b) + (b*c)

Obviously you can. I meant to make it work without needing parentheses,

but it seems that wasn't clear.