I hate to bring up possible language changes, since there is
so much of that going around.
Matz, if this is stupid, just tell me so.
I’ve sometimes wished for a “break” that would work in (almost) any
context – one that would do “the sensible thing” instead of just
giving an error saying you can’t do a break here.
Two examples are:
A long string, possibly multiline/multi-statement, is being
evaled. I want the capability to abort the eval.
I have a mild dislike for the idiom if $0 == FILE (lines) end
– because I always indent inside an if, and I don’t want to indent,
and I really just want to say: break if $0 != FILE
In both these contexts, I initially tried exit. Of course, that
doesn’t work – it exits the entire program. A “return” seems like
the next choice, but that only makes sense within a method.
There’s no proper way to do this kind of thing, as far as I can
see.
I’ve sometimes wished for a “break” that would work in (almost) any
context – one that would do “the sensible thing” instead of just
giving an error saying you can’t do a break here.
Two examples are:
A long string, possibly multiline/multi-statement, is being
evaled. I want the capability to abort the eval.
I have a mild dislike for the idiom if $0 == FILE (lines) end
– because I always indent inside an if, and I don’t want to indent,
and I really just want to say: break if $0 != FILE
I actually would like that too, especially for #2, since it avoids lots
of nasty nesting for unit tests and such.
In both these contexts, I initially tried exit. Of course, that
doesn’t work – it exits the entire program. A “return” seems like
the next choice, but that only makes sense within a method.
I think break makes sense here, and I’d use it if it were available.
There’s no proper way to do this kind of thing, as far as I can
see.
Well, maybe not proper, but here is a way to do it.
#!/usr/bin/ruby
puts “File loaded.”
if $0 == FILE then puts <<-EOF ; end
look, no indent, and we’re not nested in an if! =)
puts “File called directly.”
EOF
···
On Thursday 04 December 2003 3:13 pm, Hal Fulton wrote:
I hate to bring up possible language changes, since there is
so much of that going around.
Matz, if this is stupid, just tell me so.
I’ve sometimes wished for a “break” that would work in (almost) any
context – one that would do “the sensible thing” instead of just
giving an error saying you can’t do a break here.
Two examples are:
A long string, possibly multiline/multi-statement, is being
evaled. I want the capability to abort the eval.
I have a mild dislike for the idiom if $0 == FILE (lines) end
– because I always indent inside an if, and I don’t want to indent,
and I really just want to say: break if $0 != FILE
In both these contexts, I initially tried exit. Of course, that
doesn’t work – it exits the entire program. A “return” seems like
the next choice, but that only makes sense within a method.
There’s no proper way to do this kind of thing, as far as I can
see.
If you just do not want to indent, I would suggest
if $0 == FILE
eval DATA.readlines.join(“\n”), binding, FILE
end END
puts “HELLO”
It looks ugly and excessive, I agree. It also has problems with error
reporting, whatever line number it shows you have to add 4 (in this
particular case) to it mentally.
I have a mild dislike for the idiom if $0 == FILE (lines) end
– because I always indent inside an if, and I don’t want to indent,
and I really just want to say: break if $0 != FILE
This seems to work:
=== x.rb ===
puts “loading x.rb”
alias old_load load
def load(*args)
catch :break_from_load do
old_load(*args)
end
end
Date: Fri, 5 Dec 2003 07:13:04 +0900
From: Hal Fulton hal9000@hypermetrics.com
Newsgroups: comp.lang.ruby
Subject: Generalized break?
I hate to bring up possible language changes, since there is
so much of that going around.
Matz, if this is stupid, just tell me so.
I’ve sometimes wished for a “break” that would work in (almost) any
context – one that would do “the sensible thing” instead of just
giving an error saying you can’t do a break here.
Two examples are:
A long string, possibly multiline/multi-statement, is being
evaled. I want the capability to abort the eval.
catch/throw is pretty general:
this works:
code = <<-code
if true
def method
42
end
if not false
if true
loop do
p method
throw :bail if rand < 0.5
end
end
end
end
code
def nesting code
eval code
end
catch :bail do
nesting code
end
I have a mild dislike for the idiom if $0 == FILE (lines) end
– because I always indent inside an if, and I don’t want to indent,
and I really just want to say: break if $0 != FILE
agreed.
how about something like
TEST
for this?
In both these contexts, I initially tried exit. Of course, that
doesn’t work – it exits the entire program. A “return” seems like
the next choice, but that only makes sense within a method.
There’s no proper way to do this kind of thing, as far as I can
see.
Thoughts?
Hal
-a
···
On Fri, 5 Dec 2003, Hal Fulton wrote:
–
ATTN: please update your address books with address below!
The difference between art and science is that science is what we
understand well enough to explain to a computer.
Art is everything else.
– Donald Knuth, “Discover”
/bin/sh -c ‘for l in ruby perl;do $l -e “print "\x3a\x2d\x29\x0a"”;done’
===============================================================================
I’ve sometimes wished for a “break” that would work in (almost) any
context – one that would do “the sensible thing” instead of just
giving an error saying you can’t do a break here.
“break” or jump in general requires destination. If you want
something like “generalized break”, you have to define the destination
for each context. Basically, catch/throw is prepared for that
purpose.
A long string, possibly multiline/multi-statement, is being
evaled. I want the capability to abort the eval.
Use catch/throw.
I have a mild dislike for the idiom if $0 == FILE (lines) end
– because I always indent inside an if, and I don’t want to indent,
and I really just want to say: break if $0 != FILE
I think it’s not a good idea that preparing single syntax construct to
serve too many purpose. I admit “$0 != FILE” hack is ugly, but it
should be solved by some other way than "generalized break.
I have a mild dislike for the idiom if $0 == FILE (lines) end
– because I always indent inside an if, and I don’t want to indent,
and I really just want to say: break if $0 != FILE
This seems to work:
=== x.rb ===
puts “loading x.rb”
alias old_load load
def load(*args)
catch :break_from_load do
old_load(*args)
end
end
throw :break_from_load unless FILE == $0
puts “a”
load(FILE)
puts “b”
You get the following error when you ‘require’ this file:
irb(main):001:0> require ‘x’
loading x.rb
NameError: uncaught throw break_from_load' from ./x.rb:11:in throw’
from ./x.rb:11
from (irb):1:in `require’
from (irb):1
irb(main):002:0>
Not sure how to get around passing FILE in, or having END there
as well…
···
On Thursday 04 December 2003 5:32 pm, Ara.T.Howard wrote:
I have a mild dislike for the idiom if $0 == FILE (lines)
end – because I always indent inside an if, and I don’t want to
indent, and I really just want to say: break if $0 != FILE
I’ve sometimes wished for a “break” that would work in (almost) any
context – one that would do “the sensible thing” instead of just
giving an error saying you can’t do a break here.
“break” or jump in general requires destination. If you want
something like “generalized break”, you have to define the destination
for each context. Basically, catch/throw is prepared for that
purpose.
However sometimes having to define the destination is very inconvenient,
as in
I have a mild dislike for the idiom if $0 == FILE (lines) end
– because I always indent inside an if, and I don’t want to indent,
and I really just want to say: break if $0 != FILE
I think it’s not a good idea that preparing single syntax construct to
serve too many purpose. I admit “$0 != FILE” hack is ugly, but it
should be solved by some other way than "generalized break.
Would it be possible to wrap each file/evaluated string in an implicit
catch(:END_INTERPRETATION) do # a better name is 90% of the thing
…
end
?
···
On Fri, Dec 05, 2003 at 12:05:20PM +0900, Yukihiro Matsumoto wrote:
Not sure how to get around passing FILE in, or having END there
as well…
Yeah, I don’t think the solutions where the code comes after END
are really viable. I tend to use DATA to feed to tests, so I don’t
want DATA to be the tests.
The difference between art and science is that science is what we
understand well enough to explain to a computer.
Art is everything else.
– Donald Knuth, “Discover”
/bin/sh -c ‘for l in ruby perl;do $l -e “print "\x3a\x2d\x29\x0a"”;done’
===============================================================================
That doesn’t work in this case, because then FILE refers to
“test.rb” instead of “demo.rb”. There is probably a way to get around
that, but I haven’t tried real hard.
···
On Thursday 04 December 2003 8:32 pm, Ara.T.Howard wrote:
On Fri, 5 Dec 2003, Wesley J Landaker wrote:
Ooohh, I like that! =3D)
me too.
Not sure how to get around passing FILE in, or having END
there=20 as well…
This lets me call a file directly to test it, or have them batched for
regression test running very easily.
I’m not sure a mechanism like TEST would help me in this case
(although, it wouldn’t hurt).
···
On Thursday 04 December 2003 6:59 pm, David A. Black wrote:
Yeah, I don’t think the solutions where the code comes after END
are really viable. I tend to use DATA to feed to tests, so I don’t
want DATA to be the tests.
