[9fans] troff ignoring .eo/.ec after first time

[9fans] troff ignoring .eo/.ec after first time

[Pietro Gagliardi]

Hello. Try this:

	tbl /n/sources/contrib/pietro/plan9prog.ms | troff -ms | page

On about the third page, some code begins, but at the print()  
statement at the end there is some strangeness. If you look inside  
the .ms file, there are some .eo and .ec requests. .eo turns off \x  
and .ec turns it back on. But why is it ignored after that first  
page, which works correctly?

Re: [9fans] troff ignoring .eo/.ec after first time

[Martin Neubauer]

ms(6) says:

	Many nroff and troff
	requests are unsafe in conjunction with this package, but
	the following requests may be used with impunity after the
	first .PP: `.bp', `.br', `.sp', `.ls', `.na'.

Maybe this helps,
	Martin

* Pietro Gagliardi (pietro10@mac.com) wrote:
> Hello. Try this:
> 
> 	tbl /n/sources/contrib/pietro/plan9prog.ms | troff -ms | page
> 
> On about the third page, some code begins, but at the print()  
> statement at the end there is some strangeness. If you look inside  
> the .ms file, there are some .eo and .ec requests. .eo turns off \x  
> and .ec turns it back on. But why is it ignored after that first  
> page, which works correctly?

Re: [9fans] troff ignoring .eo/.ec after first time

[Russ Cox]

> On about the third page, some code begins, but at the print()  
> statement at the end there is some strangeness. If you look inside  
> the .ms file, there are some .eo and .ec requests. .eo turns off \x  
> and .ec turns it back on. But why is it ignored after that first  
> page, which works correctly?

assuming that /n/sourcesdump/2007/1122/contrib/pietro/plan9prog.ms
is the file in question, the first page isn't "working" correctly either,
since your

	print("hello, world\n");

turns into

	print("hello, world0);

because the \n" interpolates the " register.

the reason that .eo doesn't manage to turn this off is that
the text between .P1 and .P2 gets copied into a troff 
diversion for later processing, and that later processing
happens during the execution of .P2, by which time your idiom

	.P1
	.eo
	text
	.ec
	.P2

has restored \ as the escape character.

you can get your desired effect by doing

	.P1
	.eo
	text
	.P2
	.ec

instead.

russ