Syntax error with blocks


#1

OK guys, wtf am I doing wrong here?
The manual says I should be able to do this.

=======================

irb(main):150:0> { puts ‘foo’ }
SyntaxError: compile error
(irb):150: syntax error, unexpected tSTRING_BEG, expecting kDO or ‘{’ or
‘(’
{ puts ‘foo’ }
^
(irb):150: syntax error, unexpected ‘}’, expecting $end
from (irb):150
from :0
irb(main):151:0> { puts(‘foo’) }
SyntaxError: compile error
(irb):151: odd number list for Hash
from (irb):151
from :0
irb(main):158:0> do puts ‘foo’ end
SyntaxError: compile error
(irb):158: syntax error, unexpected kDO
do puts ‘foo’ end
^
(irb):158: syntax error, unexpected kEND, expecting $end
from (irb):158
from :0
irb(main):160:0> do; puts ‘foo’; end
SyntaxError: compile error
(irb):160: syntax error, unexpected kDO
do; puts ‘foo’; end
^
(irb):160: syntax error, unexpected kEND, expecting $end
from (irb):160
from :0


#2

On 2007-06-17 10:05:37 -0500, Oliver S. removed_email_address@domain.invalid
said:

    ^

(irb):158: syntax error, unexpected kDO
(irb):160: syntax error, unexpected kEND, expecting $end
from (irb):160
from :0

A code block is not a valid statement. If you want to create a Proc
object, use lambda.

irb(main):001:0> x = lambda { puts ‘foo’ }
=> #Proc:0x0035393c@:1(irb)
irb(main):002:0> x.call
foo
=> nil


#3

Thanks


#4

The other thing to keep in mind is that blocks are parameters passed
into methods, so they’re always associated with a method call. For
example:

10.times { puts ‘foo’ }

The block is a parameter to the times method that is being called on
the Integer 10.

Even in Banzai’s example:

x = lambda { puts ‘foo’ }

The block is passed to a method named lambda that returns a Proc of
the block passed in.

Eric

Are you interested in on-site Ruby training that uses well-designed,
real-world, hands-on exercises? http://LearnRuby.com


#5

On Jun 18, 3:11 am, ole __ removed_email_address@domain.invalid wrote:

Cool. I’m guessing something like this:

1.times { puts ‘foo’ }

or

lamba { puts ‘foo’ }.call

is never really used but could be used to achieve block scope.

If you want a more block like behavior, use begin/end

begin
puts ‘Hello from block’
end


#6

Ahhh very nice. Thanks


#7

Cool. I’m guessing something like this:

1.times { puts ‘foo’ }

or

lamba { puts ‘foo’ }.call

is never really used but could be used to achieve block scope.