使用Scheme (DrRacket) 搜索列表
所以这是我的代码：
(define *graph* (read(open-input-file "starbucks4.sxml")))
(define get-artifacts
(lambda (l)
(member (list 'opm:artifact) l)))
当我输入 get-artifacts(*graph*) 时，我收到一条错误消息 procedure application: Expected procedure, 鉴于：...(我的整个文件内容)
有人看到我做错了什么吗？谢谢大家:)
PS：我对Scheme真的很陌生，所以这可能是我忘记的一些愚蠢的语法！
So here's my code:
(define *graph* (read(open-input-file "starbucks4.sxml")))
(define get-artifacts
(lambda (l)
(member (list 'opm:artifact) l)))
When I type get-artifacts(*graph*) I get an error saying procedure application: expected procedure, given:...(the whole of my file contents)
Anyone see what I'm doing wrong? Thanks guys :)
PS: I'm really new to Scheme so it's probably some stupid syntax I'm forgetting!
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在方案中调用函数的语法是
（函数名参数），而不是函数名（参数）。当您编写
get-artifacts(*graph*)时，racket 首先评估get-artifacts，然后再评估其自身。然后它尝试计算
(*graph*)，它认为这是一个不带参数的函数调用。这是行不通的，因为*graph*是一个列表而不是一个函数。所以你会得到错误。The syntax for calling a function in scheme is
(function-name arguments), notfunction-name(arguments).When you write
get-artifacts(*graph*), racket first evaluatesget-artifactswhich evaluates to itself.Then it tries to evaluate
(*graph*), which it takes to be a function call with no arguments. That does not work because*graph*is a list and not a function. So you get the error.看我对你另一个问题的回答；看起来您正在寻找 sxpath，在这里。
See my answer to your other question; it looks like you're in search of sxpath, here.