From 139938165087002655 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,bf65828a2bbbc32e X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1993-12-14 13:09:05 PST Path: gmd.de!xlink.net!howland.reston.ans.net!pipex!uunet!ncrgw2.ncr.com!ncrhub2!torynews!ncrlnk!usglnk!uc2372c!uh2372p03.daytonoh.ncr.com!trickr From: trickr@uh2372p03.daytonoh.ncr.com (Ralph Trickey) Newsgroups: comp.std.c++ Subject: Re: bool run-time performance impact Keywords: bool Message-ID: Date: 14 Dec 93 14:43:15 GMT References: <9334701.20716@mulga.cs.mu.OZ.AU> Sender: news@uc2372c.DaytonOH.NCR.COM (News Administrative Login) Organization: NCR Lines: 28 X-Newsreader: Trumpet for Windows [Version 1.0 Rev A] >>trickr@uh2372p03.daytonoh.ncr.com (Ralph Trickey) writes: >>>3) Has anyone examined the impact on performance of mixing 2 libraries, one >>>that supports the bool keyword, and one that doesn't, and the conversions that >>>will have to take place between an int and a bool (changing non-zero to 1). I >>>am thinking of the proposed String classes et al, and legacy code. Also, the >>>problems of mistyping a variable as int instead of bool in converting code. >In article <9334701.20716@mulga.cs.mu.OZ.AU> fjh@munta.cs.mu.OZ.AU (Fergus Henderson) writes: >>You are assuming that the compiler will implement bools using a normalized >>(canonical) representation where true=1 and false=0. >>It would be quite reasonable for compilers to use a non-canonical >>representation where anything non-zero is true. In this case, >>conversion from int to bool would be a no-op. In article trickr@uh2372p03.daytonoh.ncr.com (Ralph Trickey) writes: >I understand that it is required to convert int to a bool with the value of >0 or 1. This means that converting from int to bool won't be a no-op. >Unfortunately, this means that I will be mixing old and new style bools until >ALL compiler and library vendors recognize the new keywords. Please change all "int to bool" with "bool to int" in the previous paragraph, someone pointed out in another thread that it is possible for the implementation to not store bool as a 0 or 1, but as some other values. This would probably mean converting twice, once for int to bool, and once for bool to int, but it is possible. Thanx, Ralph