Re: Ruby 1.8.6 binding value after "if" expression evaluation

Thanks. The output you report matches what I get in 1.8.6 and suggests where
to start looking for a bug. I'm not sure this is strictly related to blocks.
In particular try this:

x = 6.2*1 if
  x=6.1

The line break after the "if" is intentional since it more clearly shows
which part gets run when. In this code,
first there are two stops on the x=6.1 presumably before and after the
assignment. But by the time of the c-call to multiply 6.2*1, the value of x
is 6.1. It is like some sort of register flushing that is going before the
c-call, but again that's pure guess.

On Thu, Mar 13, 2008 at 12:59 PM, Yemi I. D. Bedu <[e-mail]> wrote:

>  Hello,
>
>  I tried this and it has to do with implicit / explicit block. Also I
> expanded example:
>
>
>
> p RUBY_VERSION
>
>
>
> def trace_func(event, file, line, id, binding, klass, *)
>
>   printf("%s:%d (%s) x=%s\n", file, line, event, eval("x", binding))
>
> end
>
>
>
> set_trace_func method(:trace_func).to_proc
>
>
>
> x=2
>
> (x=3.2) if x=3.1
>
> begin x=4.2 end if x=4.1
>
> x=5.2 if x=5.1
>
> x=6.2*1 if x=6.1*1
>
> if x=7.1 then x=7.2 end
>
> x=8
>
> x=9
>
>
>
> My Results were:
>
>
>
> "1.8.2"
>
>
>
> tt.rb:9 (line) x=
>
>
>
> tt.rb:10 (line) x=2
>
> tt.rb:10 (line) x=2
>
> tt.rb:10 (line) x=3.1
>
>
>
> tt.rb:11 (line) x=3.2
>
> tt.rb:11 (line) x=3.2
>
> tt.rb:11 (line) x=4.1
>
>
>
> tt.rb:12 (line) x=4.2
>
> tt.rb:12 (line) x=4.2
>
>
>
> tt.rb:13 (line) x=5.2
>
> tt.rb:13 (line) x=5.2
>
> tt.rb:13 (c-call) x=5.2
>
> tt.rb:13 (c-return) x=5.2
>
> tt.rb:13 (c-call) x=6.1
>
> tt.rb:13 (c-return) x=6.1
>
>
>
> tt.rb:14 (line) x=6.2
>
> tt.rb:14 (line) x=6.2
>
> tt.rb:14 (line) x=7.1
>
>
>
> tt.rb:15 (line) x=7.2
>
>
>
> tt.rb:16 (line) x=8
>
>
>
> You would need to either have parens, explicit block or use the other if
> form to get that last firing from the trace. It seems to token out each
> expression unit on a line and then call eval to get the previous lines
> value. I don't know if you can confirm this on your 1.8.6 install. The
> lines with the multiply do func calls so they eval before going into the new
> env and when the come back. You might want to have a more complex expression
> execute like a list comprehension or a map. Good day.
>
> Yemi Bedu
>
> P&R Fasteners, Inc.
> P&R Castings, LLC.
> 325 Pierce St
> Somerset, NJ 08873
> (T) 732-302-3600
> (F) 732-302-3636
>   ------------------------------
>
> *From:* Rocky Bernstein [mailto:[e-mail]]
> *Sent:* Wednesday, March 12, 2008 11:21 PM
> *To:* [e-mail]
> *Subject:* Ruby 1.8.6 binding value after "if" expression evaluation
>
>
>
> Here's another trace hook weirdness that I've encountered.
>
> Consider this program and its output:
>
> def trace_func(event, file, line, id, binding, klass, *)
>   printf("%s:%d (%s) x=%s\n", file, line, event, eval("x", binding))
> end
> set_trace_func method(:trace_func).to_proc
> x=5
> x=6.2 if x=6.1
> x=7
>
>
> $ ruby bug2.rb
> bug2.rb:6: warning: found = in conditional, should be ==
> bug2.rb:5 (line) x=
> bug2.rb:6 (line) x=5
> bug2.rb:6 (line) x=5
> bug2.rb:7 (line) x=6.2
>
> Why does x appear to have value 5 the second time on line 7 rather than
> 6.1?
>
> Looking at eval.c what's supposed to happen (I think) is that the trace
> hook is called before the expression (x=6.1) is evaluated and then called
> before the assignment "x=6.2" in which case it should have value 6.1, not
> 5.
>
> Can anyone explain why this happens?
>
> Again this is ruby 1.8.6
>