# Ruby parser wierdness?

**URL:** <https://www.ruby-forum.com/t/ruby-parser-wierdness/115115>\
**Category:** Ruby\
**Created:** [September 20, 2007, 6:58pm UTC](https://www.ruby-forum.com/t/ruby-parser-wierdness/115115 "2007-09-20T18:58:59Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ciconia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/71c47a/32.png) [@ciconia](https://www.ruby-forum.com/u/ciconia)\
**Post date:** [September 20, 2007, 6:58pm UTC](https://www.ruby-forum.com/t/ruby-parser-wierdness/115115/1 "2007-09-20T18:58:59Z")

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Hi gang

I’ve stumbled upon a weird phenomenon when trying nested Dataset#query  
methods with Sequel:

ds = DB[:items].query do  
select :x, :y  
where :x =\> DB[:stuff].query do  
select :a  
where :b =\> DB[:misc].query do  
select :c  
where :d =\> true  
end  
end  
end

#=\> /usr/local/lib/ruby/gems/1.8/gems/sequel-0.2.0.2/lib/sequel/…/  
sequel/dataset/convenience.rb:217:in `instance\_eval’: block not  
supplied (ArgumentError)

If I enclose the nested procs in parens everything works fine:

ds = DB[:items].query do  
select :x, :y  
where :x =\> (DB[:stuff].query do  
select :a  
where :b =\> (DB[:misc].query do  
select :c  
where :d =\> true  
end)  
end)  
end

It also works if I use the curly brackets notation:

ds = DB[:items].query {  
select :x, :y  
where :x =\> DB[:stuff].query {  
select :a  
where :b =\> DB[:misc].query {  
select :c  
where :d =\> true  
}  
}  
}

Is the error above the intended behavior? If it is, can someone  
explain what’s going on?

best  
Sharon

---

<div class="post-metadata">

**Author:** ![ciconia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/71c47a/32.png) [@ciconia](https://www.ruby-forum.com/u/ciconia)\
**Post date:** [September 20, 2007, 7:39pm UTC](https://www.ruby-forum.com/t/ruby-parser-wierdness/115115/2 "2007-09-20T19:39:13Z")

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On 9/20/07, Sharon R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> ```
> select :c
> 
> }
> 
> ```
> 
> }
> 
> Is the error above the intended behavior? If it is, can someone  
> explain what’s going on?

It’s a matter of the operator precedence of do and {}.

Braces bind more strongly than do (In general in Ruby symbols bind  
tighter than keywords)

irb(main):001:0\> def m1(arg)  
irb(main):002:1\> puts “m1 got block” if block\_given?  
irb(main):003:1\> end  
=\> nil  
irb(main):004:0\> def m2  
irb(main):005:1\> puts “m2 got block” if block\_given?  
irb(main):006:1\> end  
=\> nil  
irb(main):007:0\> m1 m2 {}  
m2 got block  
=\> nil  
irb(main):008:0\> m1 m2 do;end  
m1 got block  
=\> nil

So in the expression

where :x =\> DB[:stuff].query do;end

The block is being given to the where method instead of the query  
method.

–  
Rick DeNatale

My blog on Ruby  
[http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/)