Path: csiph.com!usenet.pasdenom.info!nntpfeed.proxad.net!proxad.net!feeder1-1.proxad.net!ecngs!feeder2.ecngs.de!87.79.20.101.MISMATCH!newsreader4.netcologne.de!news.netcologne.de!bcyclone01.am1.xlned.com!bcyclone01.am1.xlned.com!newsfeed.xs4all.nl!newsfeed7.news.xs4all.nl!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.042 X-Spam-Evidence: '*H*': 0.92; '*S*': 0.00; 'modify': 0.04; 'term,': 0.09; 'cc:addr:python-list': 0.10; 'python': 0.11; 'missed': 0.15; 'mathematics': 0.15; 'expressions?': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'function).': 0.16; 'well- known': 0.16; 'wrote:': 0.16; 'instance,': 0.18; 'result,': 0.18; 'stefan': 0.18; 'cc:2**0': 0.21; 'cc:addr:python.org': 0.21; 'am,': 0.23; '2015': 0.23; 'header:In-Reply-To:1': 0.24; 'written': 0.24; 'mon,': 0.24; 'message-id:@mail.gmail.com': 0.28; 'maybe': 0.31; 'common': 0.33; 'ram': 0.33; 'received:google.com': 0.34; 'replaced': 0.35; 'something': 0.35; 'but': 0.36; 'there': 0.36; 'so,': 0.37; 'difference': 0.38; 'world,': 0.38; 'mean': 0.38; 'does': 0.39; 'sure': 0.40; 'called': 0.40; 'why': 0.40; 'term': 0.60; 'learn': 0.60; 'real': 0.61; 'side': 0.62; 'world': 0.64; 'between': 0.65; 'jul': 0.72; 'chrisa': 0.84; 'influencing': 0.84; 'phenomenon': 0.84; 'pike': 0.84; 'subject: ...': 0.84; 'to:none': 0.90 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:cc :content-type:content-transfer-encoding; bh=VVeOmz4clTtMV89tNFwVEWvbyb5OVVlAjb1iHqT8DcE=; b=pEWVtx/lOZwn7EZ5ZwvfUBXb4H2XqoGeCmIBgzs1ARfOQybgQfrFx3NcEvBMjnrwTt kBVrquDK92zBaOARxJ1KCv+8gza2ojUrA4iGege9JYZz+jGj13v7wG+DWBn2aGgJv+ZC J4NlKuUNx4RN2J74gDyPrwnsTQUfkLyZwF+vhjjgaGXY2JBeCgiSb8rwgLHBZHrtiJtr eDnT8iCiIeGAJS2T1ZlIiIKLK9COg5PGbR1DmZtYlmr0wno7mIkY1gwa7rokOQBEjBGF KhMKps0D4myVNNzaDeNLGq4+3zrPW/RjDUiJVGfVAG31aw6/it3+NWYLy6EQhP7bWL6b xPHQ== MIME-Version: 1.0 X-Received: by 10.42.216.199 with SMTP id hj7mr32715725icb.11.1436143134577; Sun, 05 Jul 2015 17:38:54 -0700 (PDT) In-Reply-To: References: Date: Mon, 6 Jul 2015 10:38:54 +1000 Subject: Re: (side-)effects and ... From: Chris Angelico Cc: "python-list@python.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20+ Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 23 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1436143137 news.xs4all.nl 2882 [2001:888:2000:d::a6]:42989 X-Complaints-To: abuse@xs4all.nl X-Received-Bytes: 4475 X-Received-Body-CRC: 2737406770 Xref: csiph.com comp.lang.python:93514 On Mon, Jul 6, 2015 at 6:29 AM, Stefan Ram wrote: > But why do we not have a common and well-known term for > the counterpart, that something does not modify the state > of the world, but that the state of the world does > influence the value (behaviour) of a call such as > =C2=BBdatetime.datetime.now().time()=C2=AB? > > And this is the intention of my post: Maybe there is such > a term, and I just missed to learn it so far? So, > do you know a term for the phenomenon that can be found > in Python but not in mathematics and consists in the state > of the world influencing the value of an expressions? The Pike optimizer short-cuts this by flagging such functions as "have side effects". As far as optimizers are concerned, there's not a lot of difference between print() and time(); both of them need to be called every time they're written (unlike, for instance, math.sin(1) which can be called once and then replaced with its result, as it's a pure function). Not sure this helps, but it might indicate why there's no real term for it - "side effects" kinda can be stretched to mean both directions. ChrisA