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

Hello,

 I tried this and it has to do with implicit / explicit block. Also I
expanded example:

=20

p RUBY_VERSION

=20

def trace_func(event, file, line, id, binding, klass, *)

  printf("%s:%d (%s) x=3D%s\n", file, line, event, eval("x", binding))

end

=20

set_trace_func method(:trace_func).to_proc

=20

x=3D2

(x=3D3.2) if x=3D3.1

begin x=3D4.2 end if x=3D4.1

x=3D5.2 if x=3D5.1

x=3D6.2*1 if x=3D6.1*1

if x=3D7.1 then x=3D7.2 end

x=3D8

x=3D9

=20

My Results were:

=20

"1.8.2"

=20

tt.rb:9 (line) x=3D

=20

tt.rb:10 (line) x=3D2

tt.rb:10 (line) x=3D2

tt.rb:10 (line) x=3D3.1

=20

tt.rb:11 (line) x=3D3.2

tt.rb:11 (line) x=3D3.2

tt.rb:11 (line) x=3D4.1

=20

tt.rb:12 (line) x=3D4.2

tt.rb:12 (line) x=3D4.2

=20

tt.rb:13 (line) x=3D5.2

tt.rb:13 (line) x=3D5.2

tt.rb:13 (c-call) x=3D5.2

tt.rb:13 (c-return) x=3D5.2

tt.rb:13 (c-call) x=3D6.1

tt.rb:13 (c-return) x=3D6.1

=20

tt.rb:14 (line) x=3D6.2

tt.rb:14 (line) x=3D6.2

tt.rb:14 (line) x=3D7.1

=20

tt.rb:15 (line) x=3D7.2

=20

tt.rb:16 (line) x=3D8

=20

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]]=20
Sent: Wednesday, March 12, 2008 11:21 PM
To: [e-mail]
Subject: Ruby 1.8.6 binding value after "if" expression evaluation

=20

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=3D%s\n", file, line, event, eval("x", binding))
end
set_trace_func method(:trace_func).to_proc
x=3D5
x=3D6.2 if x=3D6.1
x=3D7


$ ruby bug2.rb
bug2.rb:6: warning: found =3D in conditional, should be =3D=3D
bug2.rb:5 (line) x=3D
bug2.rb:6 (line) x=3D5
bug2.rb:6 (line) x=3D5
bug2.rb:7 (line) x=3D6.2

Why does x appear to have value 5 the second time on line 7 rather than
6.1?=20

Looking at eval.c what's supposed to happen (I think) is that the trace
hook is called before the expression (x=3D6.1) is evaluated and then
called before the assignment "x=3D6.2" in which case it should have =
value
6.1, not 5.

Can anyone explain why this happens?=20

Again this is ruby 1.8.6=20