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Wed, 08 Jun 2022 06:12:37 -0700 (PDT) From: Taiju HIGASHI References: <20220608102124.14865-1-higashi@taiju.info> <87wndrwc5m@nckx> Date: Wed, 08 Jun 2022 22:12:34 +0900 In-Reply-To: <87wndrwc5m@nckx> (Tobias Geerinckx-Rice's message of "Wed, 08 Jun 2022 14:14:34 +0200") Message-ID: <8735gf47ul.fsf@taiju.info> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: guix-patches@gnu.org List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-patches-bounces+larch=yhetil.org@gnu.org Sender: "Guix-patches" X-Migadu-Flow: FLOW_IN X-Migadu-To: larch@yhetil.org X-Migadu-Country: US ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=yhetil.org; s=key1; t=1654694919; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:resent-cc:resent-from:resent-sender: resent-message-id:in-reply-to:in-reply-to:references:references: list-id:list-help:list-unsubscribe:list-subscribe:list-post: dkim-signature; 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spf=pass (aspmx1.migadu.com: domain of "guix-patches-bounces+larch=yhetil.org@gnu.org" designates 209.51.188.17 as permitted sender) smtp.mailfrom="guix-patches-bounces+larch=yhetil.org@gnu.org" X-Migadu-Spam-Score: 1.00 Authentication-Results: aspmx1.migadu.com; dkim=fail ("headers rsa verify failed") header.d=taiju-info.20210112.gappssmtp.com header.s=20210112 header.b=7TD88Wnp; dmarc=none; spf=pass (aspmx1.migadu.com: domain of "guix-patches-bounces+larch=yhetil.org@gnu.org" designates 209.51.188.17 as permitted sender) smtp.mailfrom="guix-patches-bounces+larch=yhetil.org@gnu.org" X-Migadu-Queue-Id: 896662C64E X-Spam-Score: 1.00 X-Migadu-Scanner: scn1.migadu.com X-TUID: uG0w6HZBhk4c Hi 写道, Thank you for reviwing! > Hi! > > Taiju HIGASHI 写道： >> The problem rarely occurs, but when we run guix commands in an >> environment >> where "less" is not installed we get an error. > > True. Odd that it's gone unreported(?) for so long. > >> I am concerned about performance degradation due to more unnecessary >> processing. > > Since you asked… :-) > > One way that this is ‘expensive’ is that it always calls WHICH at > least once, no matter what Guix was invoked to do. > > If you're familiar with Haskell or Nix: Scheme is not that, it's not > ‘lazy’ and will evaluate the (if (which "less") …) even when the > value is never used. Turning AVAILABLE-PAGER into a procedure would > avoid that. I understand that I can delay the evaluation timing if I make it a procedure, but is my understanding correct that the number of calls will remain the same because it will be evaluated each time the `call-with-paginated-output-port` procedure is called? I agree with your point that it would be better to make it a procedure, as it would be more eco-friendly to not have to evaluate when GUIX_PAGER or PAGER is specified. > Also, you're looking up the final pager in $PATH twice: you call > WHICH, but then discard its work by returning the relative string > "less". > > The final OPEN-PIPE* invokes a shell which will search $PATH again. > We could save it the trouble by returning an absolute file name: the > result of WHICH. I see, I did not understand that behavior. Thank you. > And since WHICH returns #f on failure, you can replace the nested IFs > with a single OR: > > (define (available-pager) > (or (which "less") > (which "more"))) This one is also more readable. Thank you. > And well, as you probably noticed by now, it's actually more clear and > concise if we just in-line what little is left: > > (let ((pager-command-line (or (getenv "GUIX_PAGER") > (getenv "PAGER") > (which "less") > (which "more") > ""))) > … You mean that the $PATH lookup in open-pipe can be suppressed? Also, I misunderstood the string-null? spec; available-pager should have returned an empty string. > Your original patch returns #f if no pages could be found. I don't > think that is handled, but "" is, so return that instead. > > Now I think that's 100% equivalent to your original; let me know if I > missed a spot. I thought what you said was completely correct. >> Also, if you feel that this is a minor issue and not worth >> addressing, please >> feel free to dismiss it. (Still, a fix to make the error message >> more friendly >> might be a good idea.) > > It *is* minor, but then so is the fix, and as written above it doesn't > add ‘overhead’. I think it's a good idea to check for "more" (but > no more) and silently disable paging otherwise. I will just write what you have told me, but may I continue to modify the patch? Thank, -- Taiju