line directives

[Andrew Johnson]

Does ruby support anything like #line directives in C or Perl? or
any other way to dynamically change what ruby thinks is the current
sourcefile and sourceline in its warning and error reporting?

regards,
andrew

 

[Andrew Johnson]

Note:
I'm replying to my own post as I found the following response in the
ruby-talk archives, but no replies seem to have made it through to my
c.l.r. newsfeed.

What exactly do you need it for?

This would be useful when the source code has been extracted / assembled
from another source --- in particular, literate programming. When the
extracted code is run, it is much nicer when warnings and errors point
to the relevant locations in the literate source file (which is where the
code is written and edited), rather than the extracted source file which
is executed.

regards,
andrew

 

[Gennady]

Note:
I'm replying to my own post as I found the following response in the
ruby-talk archives, but no replies seem to have made it through to my
c.l.r. newsfeed.


In [ruby-talk:96620] (http://ruby-talk.org/blade/96620), Assaph writes:

What exactly do you need it for?

This would be useful when the source code has been extracted / assembled
from another source --- in particular, literate programming. When the
extracted code is run, it is much nicer when warnings and errors point
to the relevant locations in the literate source file (which is where the
code is written and edited), rather than the extracted source file which
is executed.

regards,
andrew

If you execute your extracted code via 'eval' you can indicate a file
name and a starting line number that 'eval' will use to report errors:

----------------------------------------------------------- Kernel::eval
eval( aString [, aBinding [file [line]]]) -> anObject
------------------------------------------------------------------------
Evaluates the Ruby expression(s) in aString. If aBinding is given,
the evaluation is performed in its context. The binding may be a
Binding object or a Proc object. If the optional file and line
parameters are present, they will be used when reporting syntax
errors. As of Ruby 1.8, local variables assigned within an eval are
only available after the eval if they were defined at the outter
scope before the eval executed. In this way eval has the same
scoping rules as blocks.
def getBinding(str)
return binding
end
str = "hello"
eval "str + ' Fred'" #=> "hello Fred"
eval "str + ' Fred'", getBinding("bye") #=> "bye Fred"


Gennady.

 

[Andrew Johnson]

If you execute your extracted code via 'eval' you can indicate a file
name and a starting line number that 'eval' will use to report errors:

Well, one problem with that is that the source is extracted and assembled
from multiple locations in the literate source file(s): I'm not sure that
having the final program consist of a set of (possibly nested) eval'd
strings is a workable solution.

I'm currently thinking that a simple filter (that recognizes #line
directives) on TestUnit output may be a sufficient work-around for my
present purposes (but not really a general solution).


regards,
andrew

 

[Robert Klemme]

Does ruby support anything like #line directives in C or Perl? or
any other way to dynamically change what ruby thinks is the current
sourcefile and sourceline in its warning and error reporting?

In C one often had to correct messed up compilers - dunno why you should
need that in Ruby though. Anyway, the eval family of functions has often
additional arguments that can be used to set file and line:

http://www.rubycentral.com/book/ref_m_kernel.html#Kernel.eval

Regards

robert

 

[Jim Weirich]

In C one often had to correct messed up compilers - dunno why you should
need that in Ruby though. Anyway, the eval family of functions has often
additional arguments that can be used to set file and line:

I aways thought the line directive was used by preprocessors, so that
compile errors in the C source code would reference lines in the
preprocessor input. Ratfor did this (for example).