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From: Bakul Shah <bakul@iitbombay.org>
To: Will Senn <will.senn@gmail.com>
Cc: TUHS main list <tuhs@minnie.tuhs.org>
Subject: Re: [TUHS] v7 source code for sh
Date: Sat, 19 Feb 2022 08:06:23 -0800	[thread overview]
Message-ID: <34EEC8D8-77BD-4A44-8C30-4E1C9015F42D@iitbombay.org> (raw)
In-Reply-To: <69d88b37-5817-9a0d-4971-3d8641c2d153@gmail.com>

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https://research.swtch.com/shmacro

> On Feb 19, 2022, at 7:44 AM, Will Senn <will.senn@gmail.com> wrote:
> 
>  I have been poring through the v7 source code lately, and came across an oddity I would like to know more about. Specifically, in sh. The code for sh is c, but it makes extensive use of of macros, for example:
> /usr/src/cmd/sh/word.c
> ...
> WHILE (c=nextc(0), space(c)) DONE
> ...
> 
> The macros for sh are defined in mac.h:
> /usr/src/cmd/sh/mac.h
> ...
> #define BEGIN   {
> #define END     }
> #define SWITCH  switch(
> #define IN      ){
> #define ENDSW   }
> #define FOR     for(
> #define WHILE   while(
> #define DO      ){
> #define OD      ;}
> #define REP     do{
> #define PER     }while(
> #define DONE    );
> ...
> I can read the resultant code through the lens of my experience coding c, but I'm curious why the macros and how this came about? In v6, the sh source is straight up c. Is there a story behind it worth knowing?
> 
> Thanks,
> 
> Will

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  parent reply	other threads:[~2022-02-19 16:07 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-19 15:43 Will Senn
2022-02-19 16:03 ` Steve Nickolas
2022-02-19 16:07   ` Clem Cole
2022-02-19 16:43   ` Steve Nickolas
2022-02-19 17:24   ` Ron Natalie
2022-02-19 16:04 ` Clem Cole
2022-02-19 16:06 ` Bakul Shah [this message]
2022-02-19 16:57   ` Will Senn
2022-02-19 17:44 Bakul Shah
2022-02-19 18:44 ` Rob Pike
2022-02-19 19:29   ` Clem Cole
2022-02-19 22:39   ` John Cowan
2022-02-19 23:11     ` Sven Mascheck
2022-02-19 23:34       ` Rob Pike
2022-02-19 23:36       ` silas poulson
2022-02-20 20:54       ` Chet Ramey
2022-02-20 21:02         ` Larry McVoy
2022-02-20 21:19           ` Chet Ramey
2022-02-20 21:19         ` Lyndon Nerenberg (VE7TFX/VE6BBM)
2022-02-20 22:39           ` Chet Ramey
2022-02-21  1:01             ` Dan Cross
2022-02-22  4:54               ` Dan Stromberg
2022-02-22  5:39                 ` Rob Pike
2022-02-22  5:54                   ` George Michaelson
2022-02-20  7:24 Rudi Blom
2022-02-21 17:58 Norman Wilson
2022-02-21 18:10 ` Rob Pike
2022-02-22  3:07 Brian Walden
2022-02-22 14:28 ` Chet Ramey
2022-02-22 14:47 ` Clem Cole

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