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comp.lang.ruby

Suppressing printing of evaluated expressions in irb

Michael Hartl

3/20/2006 11:10:00 PM

I've looked all over, but I can't figure out how to suppress the
printing of evaluated expressions in irb. Ordinarily, this is no
problem:

irb(main):001:0> a = []
=> []

But what if the thing returned is huge?

irb(main):001:0> b = function_returning_something_huge
<disaster>

In Python, the interpreter suppresses the printing of the expression if
there is assignment, but not otherwise:

>>> a = []
>>> a
[]
>>> b = function_returning_something_huge()
>>> b
<disaster, but I asked for it!>

How do I get the same or similar behavior in irb?

Thanks in advance,

Michael
6 Answers

Timothy Bennett

3/21/2006 12:25:00 AM

0


On Mar 20, 2006, at 3:13 PM, Michael Hartl wrote:

> I've looked all over, but I can't figure out how to suppress the
> printing of evaluated expressions in irb. Ordinarily, this is no
> problem:
>
> irb(main):001:0> a = []
> => []
>
> But what if the thing returned is huge?
>
> irb(main):001:0> b = function_returning_something_huge
> <disaster>
>

In irb, enter `conf.return_format = ""` That'll turn off all
printing of evaluations in irb, which means you have to use `puts` if
you want to see any results, but it'll avoid your disasters.

You can add 2 methods to your .irbrc if you like, one that clears the
formatting with the line I gave, and one that sets it back to normal
(the default is "=> %s\n"), so that you can switch back and forth
between the two modes easily.

There may be a better solution, but this is all I came up with.
Still, I hope it helps.

Tim

Timothy Bennett

3/21/2006 12:37:00 AM

0


On Mar 20, 2006, at 4:25 PM, Timothy Bennett wrote:
> There may be a better solution, but this is all I came up with.
>

There is another solution, that of course I realize after I send out
the message. You can set conf.return_format to "=> %0.100s\n", where
the number after the . (in this case 100), is the maximum number of
characters you want printed to the screen.

Tim

Nate Smith

3/21/2006 1:12:00 AM

0

Hello everyone,

I'm trying to keep a thread alive after exiting a method. The pseudo-
code is as follows:

class A

def start
@mainThread = Thread.new {
oneThread = Thread.new {
# do some stuff
}
twoThread = Thread.new {
# do some other stuff
}
oneThread.join
twoThread.join
}
end
end

aObject = A.new
aObject.start


The problem is that since there is no :join call on @mainThread, it
is killed (and hence oneThread, and twoThread as well) once control
ends in :start. This is perfectly valid, of course, but I would like
@mainThread to stay alive after control in :start ends. Is there any
way to do this? Thanks

Nate

Caleb Clausen

3/21/2006 1:20:00 AM

0

On 3/20/06, Michael Hartl <mhartl@gmail.com> wrote:
> I've looked all over, but I can't figure out how to suppress the
> printing of evaluated expressions in irb. Ordinarily, this is no
> problem:
>
> irb(main):001:0> a = []
> => []
>
> But what if the thing returned is huge?
>
> irb(main):001:0> b = function_returning_something_huge
> <disaster>

If you want to suppress printing for just one line, try appending ';0'
to the end of the command:

irb(main):001:0> b = function_returning_something_huge;0
=> 0

Joel VanderWerf

3/21/2006 1:51:00 AM

0

Nate Smith wrote:
> Hello everyone,
>
> I'm trying to keep a thread alive after exiting a method. The
> pseudo-code is as follows:
>
> class A
>
> def start
> @mainThread = Thread.new {
> oneThread = Thread.new {
> # do some stuff
> }
> twoThread = Thread.new {
> # do some other stuff
> }
> oneThread.join
> twoThread.join
> }
> end
> end
>
> aObject = A.new
> aObject.start
>
>
> The problem is that since there is no :join call on @mainThread, it is
> killed (and hence oneThread, and twoThread as well) once control ends in
> :start. This is perfectly valid, of course, but I would like @mainThread
> to stay alive after control in :start ends. Is there any way to do this?
> Thanks
>
> Nate
>

Is you program exiting after aObject.start? Then maybe you want to do
@mainThread.join at that point?

The @mainThread should still be alive, until the program exits, unless
it has suffered an exception.

Do you have Thread.abort_on_exception = true?

--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

Michael Hartl

3/27/2006 11:09:00 PM

0

Thanks for your help. Tim's suggestions are nice, but I'd prefer to be
able to make the print/no-print decision on the fly, on a per-statement
basis. On these grounds, Caleb's suggestion meets my needs best. I
had actually tried using a semicolon, but of course irb then just waits
for the next statement. Putting a 0 (or anything else) is a bit of a
kludge compared to the Python interpreter's convention, but it gets the
job done.

Thanks,

Michael