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Re: Help with map match

From: Ricardo Wurmus
Subject: Re: Help with map match
Date: Fri, 30 Nov 2018 03:45:17 +0100
User-agent: mu4e 1.0; emacs 26.1


> I want the procedure to return #t if a match is found and I want it to
> match if it begins with the same e.g. "rollup-plugin" should match
> "rollup-plugin-node-resolve" and return #t
> Else #f

> This did not work:
> (use-modules (ice-9 match))
> (define x
>         '("ts" "test"))
> (map (match x
>         ("test") #t)
>         (else #f) x)

“map” requires a procedure and a list as its arguments, applies the
procedure to every element and then returns a new list with the results.

Since you just want a single boolean as the return value you may want to
use “any” instead, which tells you if a procedure returned #t for “any”
of the items in a list.

--8<---------------cut here---------------start------------->8---
(use-modules (srfi srfi-1))

(define (blacklisted? pkg-name)
  (string-prefix? "rollup-" pkg-name))

(any blacklisted?
 '("rollup-plugin" "rollup-plugin-foo")) ; => #t

(any blacklisted?
 '("all" "is" "good")) ; => #f
--8<---------------cut here---------------end--------------->8---

“blacklisted?” can then implement whatever logic you need.


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