Problem: ifelse ifelse define conbination

[Jan Jansen]

Dear M4 support person,

 

My name is Jan Jansen and I supply my full contact details below with this E-mail. As in the header of this E-mail indicated, I would like to report a problem that I have, not a bug because the documentation does not state that it should work, although I thought (wrongly?) that it would. In the manual you ask for the version number of my rather old M4:

   $ m4 --version

   m4 (GNU M4) 1.4.17

   Packaged by Cygwin (1.4.17-1)

   Copyright (C) 2013 Free Software Foundation, Inc.

   License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.

   This is free software: you are free to change and redistribute it.

   There is NO WARRANTY, to the extent permitted by law.

  

   Written by Rene' Seindal.

 

Please find attached to this E-mail the M4 source file, TestIfelseDefine.m4, that is completely documented and should explain itself. The idea is to make a define() or perhaps better redefine command dependent on some condition and use an ifelse(…,…,define(),define()) statement for that and demonstrate and document that it works. As the conditions became more complex, I decided to use a ifelse(…,…,ifelse(…,…,define())) statement for that and it did not work. I am surprised that it did not work but found in the manual no statement that it should work. I have tested with text without define() that the statement works and I have provided a work-around. This means that M4 is still usable if the double ifelse define statement is not supported, although the final program looks worse and is less easy to support. My question too you is, am I miss using M4, it is trying to use it for something that it is not supposed to do? As for as I know the C-preprocessor allows such constructs, even deeply nested and therefore I assumed M4 would do that too. My other question is, why does M4 supported it as ifelse define combination but not the more deeply nested ifelse ifelse define combination? I would have expected that if the first works the others would be done by the M4-program nearly automatically. My last question is, do you consider my supplied M4 source files as being portable? I use the same program on a lot of different machines and I would like the output to be the same on all those machines. I program and test my M4 source code on my office PC but the actual program runs on a production PC-Cluster.

 

As you can read, I am using the M4 program with a lot of pleasure and I am enjoying that it is wide availability in the UNIX world. I use it for one of my projects intensively and it makes my work a lot easier. I would like to thank you for that. I also would like to thank you for all the time you spend in answering my questions. I hope that this E-mail can make M4 a better program or that my knowledge of M4 can be increased.

 

With best regards,

Jan

 

 

Dr. Jan T.M. Jansen

Medical Dosimetry Group

Radiation Dosimetry Department

Centre for Radiation, Chemical and Environmental Hazards

Public Health England

Chilton, Didcot

Oxon, OX11 0RQ, UK

Tel: +44 (0) 1235 825017

Fax: +44 (0) 1235 834925

E-mail: address@hidden

Website: http://www.gov.uk/phe

 

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TestIfelseDefine.m4
Description: TestIfelseDefine.m4