Lambda block doesn't work with upto iterator

Hi Folks,

I’m new to Ruby and I’m trying to get a complete understanding of
blocks. I
captured some code in a block using lambda and was able to execute the
code
with the .time Integer iterator, but I get an exception trying to get it
to
work with the .upto iterator. The code is below. Can anyone explain why
the
.upto call fails but the .times call succeeds.

Excerpt:

proc1 = lambda do |p1|
puts “#{p1}”
end

This works.

5.times &proc1

Why does this fail?

0.upto(4) &proc2

Thanks,

Ed

Full Code:

Experiment with blocks!

Tried with ruby verion: ruby 1.8.6 (2007-09-24 patchlevel 111)

[i386-mswin32]

Ed Loyot

proc1 = lambda do |p1|
puts “#{p1}”
end

proc2 = Proc.new do |p1|
puts “#{p1}”
end

Make sure the proc works.

puts “Call proc1!”
proc1.call “112”

puts “Call proc2!”
proc2.call “212”

Try it with an iterator.

puts “Call proc1 with times iterator!”
5.times &proc1

puts “Call proc2 with times iterator!”
5.times &proc2

Why does this fail?

begin
puts “Call proc1 with upto iterator!”
0.upto(4) &proc1
rescue StandardError => error
puts "Caught error: " + error
end

Why does this fail?

begin
puts “Call proc2 with upto iterator!”
0.upto(4) &proc2
rescue StandardError => error
puts "Caught error: " + error
end

Ed Loyot wrote:

Why does this fail?

0.upto(4) &proc2

It has to be 0.upto(4,&proc2) or 0.upto 4, &proc2
In other words: syntax-wise a &-proc is treated like just another
argument
(although it has to come last in the argument list), not like a block.

HTH,
Sebastian

On 17/01/2008, Ed Loyot [email protected] wrote:

This works.

5.times &proc1

Why does this fail?

0.upto(4) &proc2

0.upto(4,&proc2)

Farrel

5.times &proc2
is the same as
5.times(&proc2)

0.upto(4) &proc1
change to
0.upto(4, &proc1)

It should works.
I guess that “0.upto(4) &proc1” is parsed by Ruby like bitwise and
with left operand “0.upto(4)” and right operand “proc1”.


Rados³aw Bu³at

http://radarek.jogger.pl - mój blog

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs