functional programming - Can functions with non-pure arguments of type functions be pure? -


can functions take non-pure functions arguments considered pure if not change/store state directly, don't reference global variables etc? , how draw line on pure , not, solely on function's in question code or take account effects of invoking arguments?

e.g. imagine scenario, pure function represents stateless workflow , takes arguments few actions executed during workflow. 1 of these actions changes state somewhere. if i'm looking strictly @ implementation of workflow, seems pure, modify state invoking parameter function modifies state. i'm tempted speculate workflow non-pure, passing in different argument not change state make pure, i'm confused.

any appreciated. thank you.

(define (its-not-me launch-rockets)    (lambda ()        (launch-rockets)))

is indeed pure. doesn't launch rockets, constructs computation will, if called. no side effects caused merely constructing such computation.

(define (it-is-me launch-rockets)    (launch-rockets)    ((its-not-me launch-rockets)))

does indeed launches rockets, twice. whether directly or indirectly, doesn't matter. if causes side effects during execution, causes side effects during execution.

and if have

(define (launch-rockets)    (if (prime? (random-integer))       (do-actually-launch-rockets)       (list 'do-nothing)))

nothing changes. first still pure, constructing computation potentially causing side-effects, impure.

even 

(define (launch-rockets)    (if (prime? (random-integer))      (list 'i-am-only)      (list 'kidding)))

isn't pure function, uses non-pure effect, randomness. pure functions return same result same arguments.


Comments

Post a Comment

Popular posts from this blog

javascript - jQuery: Add class depending on URL in the best way -

i have html progress meter: <div class="col-md-3" style="margin-left: -20px;"> <div class="progress-pos active" id="progess-1"> <div class="progress-pos-inner"> login </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-2"> <div class="progress-pos-inner"> scan items </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-3"> <div class="progress-pos-inner"> confirm address </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-4"> <div class="progress-pos-in...
Read more

caching - How to check if a url path exists in the service worker cache -

i need check if particular url path exists in service worker cache. example, suppose url is: /myserviceworker/service?a=110&b=70 this url exists in cache, there many of them different values of , b. now, suppose want refresh of these urls, how can that? i want know how access key values service worker cache. if know key, plan follows: var url = new url(key); if(url.pathname === "\/myserviceworker/service") refetch key but not sure how cache key , in format is. mean, string or url? cache api has match() method returns promise resolving in response object if match or undefined if no match exists. second parameter object can specify ignoresearch not take account url parameters. the ignoresearch option supported firefox ( chrome status here ). in other hand, retrieve cache entries, can use keys() method.
Read more

Redirect to a HTTPS version using .htaccess -

i need modify .htaccess file redirect urls https version without "www". http://example.com --> https://example.com http://www.example.com --> https://example.com https://www.example.com --> https://example.com this how .htaccess file looks like: rewriteengine on rewritecond %{request_filename} !-d rewritecond %{request_filename} !-f rewriterule ^(.*)$ redirect.php?id=$1&page=$2 [qsa,l] what modifications need make .htaccess in order forward https without "www"? it depends on doing current code. looks file called redirect trying display php page seo friendly url. think might confusing people. anyway, need , force https without www, need 1 more rule above. also second rule needs two capture groups in rewriterule test string because wanting 2 different values using $1 , $2 references. rewriteengine on #rediect www non www and/or http https --- combinations. rewritecond %{http_host} !^example\.com [nc,or] rewritecond %{https} !^...
Read more