racket

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Can not make rendering of html <select><option value="id".... with select-input formlet

I trying to use select-input formlet to render an <开发者_JS百科SELECT ...><OPTION value=\"1\">item1</OPTION><OPTION value=\"2\">item2</OPTION></SELECT>[详细]

2023-04-13 04:28 分类：问答
Sum of numbers in a list using Scheme

I want to sum the numbers in a list without using recur开发者_如何学Csion. I know you can sum a list of numbers like this[详细]

2023-04-12 10:02 分类：问答
SICP Video Lecture 2

I have a problem with this example (define (+ x y) (if (= x 0) y (+ (-1+ x) (1+ y)))) What is the problem with -1+ and 1+, when i evaluate it i get this result[详细]

2023-04-11 19:51 分类：问答
exception: current-continuation-marks: no corresponding prompt in the continuation: #<continuation-prompt-tag:web>

why do i get exception on (redirect/get) in this program #lang web-server (require web-server/formlets web-server/page) (struct app (nm) #:mutable)[详细]

2023-04-09 20:17 分类：问答
Passing an empty list to a defined-type: possible?

A rookie Racket question. I\'m using Krishnamurthi\'s PLAI textbook for this one, and the associated Racket programming language.[详细]

2023-04-05 23:16 分类：问答
Scheme: Lists of three dotted elements returning strangely (like an infix operator?)

I am a new Scheme/Racket student, so please excuse any blatant syntax errors. It came up in class today that the scheme list \'(a, b, c) should be invalid, but when we ran it, it returned:[详细]

2023-04-05 05:33 分类：问答
Iterating in Scheme

Let\'s say that I have a list of lists in Scheme, like so: (define a-list(list (list a b) (list c d) (list e f) (list g h) (list i j)))[详细]

2023-04-05 04:43 分类：问答
mappend! can't append element to the list if the list is empty?

(require racket/mpair) (define (bld-mlst . args) (list->mlist args)) (define mlst-my (bld-mlst)) mlst-my[详细]

2023-04-03 15:09 分类：问答
Dynamically find out how many inputs a function has, Racket

Is there a way to find out at ru开发者_Go百科ntime, how many inputs (arguments, parameters) a function has?[详细]

2023-04-03 04:25 分类：问答
Racket: using events in a frame% window

I\'m learning Racket (formerly PLT Scheme, a LISP dialect) and try to discover how to handle events different than paint-callback (maybe it\'s not even one).[详细]

2023-04-02 09:35 分类：问答