On Tue, May 25, 2010 at 8:48 PM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > At Tue, 25 May 2010 17:31:43 -0400, Carl Eastlund wrote: >> #lang racket >> (define rx #px"(\\d*)d(\\d+)([+-]\\d+|)") >> (match (current-command-line-arguments) >> [(vector (regexp rx (list _ dice sides mod))) >> (apply + (or (string->number mod) 0) >> (build-list (or (string->number dice) 1) >> (λ (i) (+ 1 (random (string->number sides))))))]) > > Impressively compact! But there's really a lot going on there. > > Dice make a good example for a simple command-line utility. Here's a > simpler program that is inspired by your example: > > #lang racket > ;; A dice-rolling command-line utility > (require racket/cmdline) > (command-line > #:args (sides dice) > (for ([i (in-range (string->number dice))]) > (displayln (random (string->number sides)))))
#lang racket ;; A dice-rolling command-line utility (require racket/cmdline) (command-line #:args (dice sides) (for ([i (in-range (string->number dice))]) (displayln (+ 1 (random (string->number sides)))))) This version puts "dice" and "sides" in the more canonical order, for those of us used to writing both down consistently. I also fixed your off-by-one error in calling "random". I'm kind of sad to give up the regexp matching, but I see another example has that covered. No one appears to have big-bang so far, so here's the best I can come up with in 7 lines: #lang htdp/bsl (require 2htdp/image) (require 2htdp/universe) ;; Blow up a big red balloon before it deflates. (define (balloon b) (circle b "solid" "red")) (define (blow-up b k) (+ b 5)) (define (deflate b) (max (- b 1) 1)) (big-bang 50 (on-key blow-up) (on-tick deflate) (to-draw balloon 200 200)) --Carl _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
