RE: m4 process hang

[Verma, Nitin \(GE Consumer & Industrial\)]

Even this feed will hang.

---------------

define(`x', `y')
x
define(`y', `x')
y

---------------

It's a infinite loop, y expands to x then x expands to y then y expands to x ... and so on so for

 

Am I right?

 

and better way to write this feed is:

 

-----------------

define(`x', ``y'')
x
define(`y', ``x'')
y
-----------------

 

or

 

My old feed as

------------------

define(`x', `y')
x
define(x, ``y'')
y

------------------

i.e:

x = y

y = `y'

so, now y's expansion is y quoted

 

not

------------------

define(x, y)
x
define(x, y)
y

------------------

i.e.

x=y

y=y

so, now y's expansion is y unquoted ... and the problem starts

 

 

-----Original Message-----
From: address@hidden [mailto:address@hiddenOn Behalf Of Verma, Nitin (GE Consumer & Industrial)
Sent: Wednesday, May 26, 2004 9:37 PM
To: address@hidden
Subject: m4 process hang

Hi Team,

 

I am very new to m4 macros, I effort to learn m4 macro writing. I can across this behavior.

I just made a file `try'

 

[neo]$ cat try
define(x, y)
x
define(x, y)
y
[neo]$

 

And fed to m4

 

[neo]$ m4 try

 

y

 

 

(hangs)

 

Now if I write

 

[neo]$ cat try

define(x, y)
x
define(x, y)

[neo]$

 

and the feed to m4

 

[neo]$ m4 try

 

y

 

[neo]$

 

it works as expected.

Am I doing something wrong?

 

[neo]$ m4 --version
GNU m4 1.4.1
[neo]$

 

Regards,

 

Nitin