racket

I'm trying to hook up URL dispatch with Racket (formerly PLT Scheme). I've taken a look at the tutorial and the server documentation. I can't figure out how to route requests to the same servlets. Specific example: #lang scheme (require web-server/servlet) (require web-server/dispatch) (provide/contract (start (request? . -> . response/c))) (define (start request) (blog-dispatch request)) (define-values (blog-dispatch blog-url) (dispatch-rules (("") list-posts) (("posts" (string-arg)) review-post) (("archive" (integer-arg) (integer-arg)) review-archive) (else list-posts))) (define (list-posts

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I'm trying to get Geiser's REPL to work in Emacs, but it doesn't seem to be able to find Racket. racket is on my path, but anytime I type run - geiser followed by racket it complains: Unable to start REPL: Searching for program: no such file or directory, racket I read in the Geiser docs that I may have to manually tell Geiser where to find racket , but I can't tell where to configure this property of Geiser. Thanks for your help. 回答1: Ok, so I added: ( setq geiser - racket - binary "/home/user/racket/bin/racket" ) to my .emacs

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am just trying to do very simple code with set-car! and set-cdr! in racket , but I got the error: expand: unbound identifier in module in: set-car! and expand: unbound identifier in module in: set-cdr! Aren't they defined in racket ? Could anyone help? 回答1: You need to import mutable-pairs-6 , like this: (require rnrs/mutable-pairs-6) Those procedures were moved to a different module and renamed to mcons , mcar , mcdr , set-mcar! , set-mcdr! , mlist to emphasize that they operate on mutable data, unlike their immutable counterparts. 回答2:

In Python, I can do something like this: t = (1, 2) a, b = t ...and a will be 1 and b will be 2. Suppose I have a list '(1 2) in Scheme. Is there any way to do something similar with let ? If it makes a difference, I'm using Racket. In racket you can use match , (define t (list 1 2)) (match [(list a b) (+ a b)]) and related things like match-define : (match-define (list a b) (list 1 2)) and match-let (match-let ([(list a b) t]) (+ a b)) That works for lists, vectors, structs, etc etc. For multiple values, you'd use define-values : (define (t) (values 1 2)) (define-values (a b) (t)) or let

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm guessing that #lang racket is a dialect of scheme with much more out of the box structures and common functions and perhaps would be more pedagogic. What are the perks a #lang racket against #lang scheme? Is it best (or even possible) to use #lang scheme in racket to follow all the content of 'Structure and Interpretation of Computer Programs' or even 'How to Design Programs'. HtDP is #lang racket specific? Whatever code written in #lang scheme, as long as libraries are not being included, can be used in chicken scheme or any main