<div class="gmail_quote">On Thu, Dec 23, 2010 at 2:26 AM, Todd O'Bryan <<a href="mailto:toddobryan@gmail.com">toddobryan@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> I just realized something. You probably speak British (or at least un-American) English. One of my former students from Manchester said the first two weeks of math were very confusing because what we call parentheses he called brackets and what we called brackets, he called something else. Here's an English to English dictionary: ( and ) = open and close parentheses [ and ] = open and close brackets { and } = open and close (curly-)braces You tend to use parentheses in Racket, except in some special forms, which use brackets instead. (These occur when you'd have a couple of parentheses in a row and are just there to make visual parsing easier.) Hope that helps, Todd <div><div></div><div class="h5"> On Wed, Dec 22, 2010 at 10:22 AM, Todd O'Bryan <<a href="mailto:toddobryan@gmail.com">toddobryan@gmail.com</a>> wrote: > Here's an algorithm for converting from "normal math" to Racket. > > Write your expression: > > people * ticket-price - (number-of-shows * 20 + people * ticket-price) > > Notice that I didn't put parentheses anywhere that order of operations > didn't require them. > > Now, add exactly one pair of parentheses for every operator that > doesn't have one. Make sure you don't add too many and make sure you > don't add too few. You should end up with the same number of operators > as pairs of parentheses: > > ((people * ticket-price) - ((number-of-shows * 20) + (people * ticket-price))) > > Notice 5 operators (*, -, *, +, and *), 5 open parens, and 5 close parens. > > Now, move each operator to right after the open paren of the pair that > encloses it. In other words, I'll move the first * to in front of > people (i.e. after the second open parenthesis), but the - will move > after the first open parenthesis. > > (- (* people ticket-price) (+ (* number-of-shows 20) (* people ticket-price))) > > Don't worry. This gets much easier with practice. > > Todd > > On Wed, Dec 22, 2010 at 5:44 AM, Sayth Renshaw <<a href="mailto:flebber.crue@gmail.com">flebber.crue@gmail.com</a>> wrote: >> What I am having trouble navigating is the brackets. >> >> Simply in normal math what I am trying to do is >> >> (people * ticket price)-((number of shows * 20)+(people * cost per person)) >> >> Contrcat : total profit : attendees performance -> number >> >> ;; Purpose to calculate total profit of a theatre per show >> >> ;;Example: (total profit 20 1) should produce $70 >> >> ;;Defintion: ( define (- profit cost)) >> (* patrons 5( - (* patrons 0.5(+ (* shows 20))))) >> >> (define (patrons p) >> ;p a number >> ... >> ) >> >> (define (shows s) >> ;s a number >> ... >> ) >> >> (define (total_profit p s) >> (* p 5( - (* p 0.5(+ s 20))))) >> >> >> >> _________________________________________________ >> For list-related administrative tasks: >> <a href="http://lists.racket-lang.org/listinfo/users" target="_blank">http://lists.racket-lang.org/listinfo/users</a> >> > </div></div></blockquote></div> Thanks for the tip on the parentheses. Having a close and open without an operator " ) ( " between them really through me. Yes I speak Australian/British English this hasn't been too much of a hurdle though in HTDP I wont be doing Ex 2.3.1 as I have no idea about nickels and dimes. The book is very good regardless of that minor localisation. Sayth