# Fwd: parse tree redux

**URL:** <https://www.ruby-forum.com/t/fwd-parse-tree-redux/125066>\
**Category:** Ruby\
**Created:** [January 4, 2008, 11:44pm UTC](https://www.ruby-forum.com/t/fwd-parse-tree-redux/125066 "2008-01-04T23:44:34Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [January 4, 2008, 11:44pm UTC](https://www.ruby-forum.com/t/fwd-parse-tree-redux/125066/1 "2008-01-04T23:44:34Z")

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somehow missent

---------- Forwarded message ----------

More issues with this. Context in forwarded msg.

Here’s a (probably very naive) implementation of the discussed code.  
It takes code blocks, turns them into individual statements, and  
module\_evals each individual statement. It does this by turning blocks  
into code with Ruby2Ruby, splitting the code on new lines, and  
module-eval()ing each statements in the resulting array.

If you think about it the problem is obvious. Here’s the code.

```
def generate(&block)
  code = ""
  statements_in_the_block(block).each do |statement|
    code << Generators.module_eval(statement)
  end
  code
end
def statements_in_the_block(block)
  statements = /proc 

```

{\n(.+)}/m.match(block.to\_ruby)[1].split(/\n/)  
statements.map {|statement| statement.gsub!(/^\s+/, “”)}  
statements.map {|statement| statement.gsub!(/\s+/, " ")}  
statements  
end

The problem, of course, is nested blocks. If you hit a block which  
contains another block, you get eval trying to eval block-starting  
lines like

eval(“block\_taking\_method do |variable|”)

which of course goes bonk.

Probably what I need to do instead (thinking out loud) is pull the  
blocks and statements out of the actual s-exps, like have some method  
which takes s-exps and then turns them into blocks and statements, and  
work from there. Ironically the blocks it’s breaking on do fine, due  
to a quirk in my code, the inner blocks are good but the larger blocks  
break.

–  
Giles B.

Podcast: [http://hollywoodgrit.blogspot.com](http://hollywoodgrit.blogspot.com)  
Blog: [http://gilesbowkett.blogspot.com](http://gilesbowkett.blogspot.com)  
Portfolio: [http://www.gilesgoatboy.org](http://www.gilesgoatboy.org)  
Tumblelog: [http://giles.tumblr.com](http://giles.tumblr.com)

---------- Forwarded message ----------  
From: Giles B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Date: Jan 4, 2008 8:07 AM  
Subject: Re: parse tree?  
To: ruby-talk ML [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

> > > > def code\_for █ block.to\_ruby; end  
> > > > =\> nil  
> > > > code\_for do  
> > > > ?\> single\_line(statement)  
> > > > statement(:which =\> spans,  
> > > > ?\> :multiple =\> lines)  
> > > > end  
> > > > =\> “proc {\n single\_line(statement)\n statement(:which =\>  
> > > > spans, :multiple =\> lines)\n}”
> 
> There are clean ways to ensure it isn’t a proc as well.

That totally solves my problem. Or at least, _ **if** _ it’s guaranteed  
to turn multi-line statements into one-liners every time, that very  
probably totally solves my problem. (I haven’t tried it yet, I’ve just  
proved it to be true, etc.) I can just pull it out of the proc{} with  
a regex and then split it on the newlines. Baddabing baddaboom.

–  
Giles B.

Podcast: [http://hollywoodgrit.blogspot.com](http://hollywoodgrit.blogspot.com)  
Blog: [http://gilesbowkett.blogspot.com](http://gilesbowkett.blogspot.com)  
Portfolio: [http://www.gilesgoatboy.org](http://www.gilesgoatboy.org)  
Tumblelog: [http://giles.tumblr.com](http://giles.tumblr.com)

–  
Giles B.

Podcast: [http://hollywoodgrit.blogspot.com](http://hollywoodgrit.blogspot.com)  
Blog: [http://gilesbowkett.blogspot.com](http://gilesbowkett.blogspot.com)  
Portfolio: [http://www.gilesgoatboy.org](http://www.gilesgoatboy.org)  
Tumblelog: [http://giles.tumblr.com](http://giles.tumblr.com)

---

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**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [January 5, 2008, 8:47am UTC](https://www.ruby-forum.com/t/fwd-parse-tree-redux/125066/2 "2008-01-05T08:47:19Z")

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On Jan 4, 2008, at 14:44 , Giles B. wrote:

> ```
> statements = /proc \{\n(.+)\}/m.match(block.to_ruby)[1].split(/ 
> 
> ```
> 
> \n/)  
> statements.map {|statement| statement.gsub!(/^\s+/, “”)}  
> statements.map {|statement| statement.gsub!(/\s+/, " ")}  
> statements  
> end

I still don’t understand the 1-line obsession… and yes, that is  
naive, it’ll break on strings, sub-procs, pretty much all blocks, etc.  
You can’t treat “statements” in ruby as each line of a block. #to\_ruby  
is probably not what you want.

---

<div class="post-metadata">

**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [January 5, 2008, 9:04am UTC](https://www.ruby-forum.com/t/fwd-parse-tree-redux/125066/3 "2008-01-05T09:04:15Z")

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Ryan D.:  
i recently started playing with Parsetree and Ruby2Ruby and Ruby2C,  
what’s bugging me it’s compleate lack of wiki/documentation - i read  
your blog - but it’s hard to distinguish stuff that’s still related from  
obsolete.

aside from that, code you wrote is plain amazing 🙂

and i already have few idea’s how to use it ^^

---

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**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [January 5, 2008, 8:35pm UTC](https://www.ruby-forum.com/t/fwd-parse-tree-redux/125066/4 "2008-01-05T20:35:48Z")

</div>

On Jan 5, 2008, at 00:03 , Marcin R. wrote:

> i recently started playing with Parsetree and Ruby2Ruby and Ruby2C,  
> what’s bugging me it’s compleate lack of wiki/documentation - i read  
> your blog - but it’s hard to distinguish stuff that’s still related  
> from obsolete.
> 
> aside from that, code you wrote is plain amazing 🙂
> 
> and i already have few idea’s how to use it ^^

complete lack of documentation?!? I write developer tools. I basically  
expect my user base to be able to read code and I try to write the  
clearest, smallest code possible such that often doco isn’t necessary.  
But in this case I’m a bit confused:

```
 http://parsetree.rubyforge.org/ParseTree/ !!!

```

the doco is actually pretty good (coverage wise–I can’t judge the  
content as I don’t read it), ~60% according to dcov and it is beating  
me up on things like my error classes.

---

<div class="post-metadata">

**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [January 5, 2008, 8:49pm UTC](https://www.ruby-forum.com/t/fwd-parse-tree-redux/125066/5 "2008-01-05T20:49:50Z")

</div>

> 

Hmmm. Problem is that sometimes when you look for a solution for certain  
problem it’s nice if you have short introduction on how to use it.

If you have to evaluate 3-5 solutions and you have to get to know each  
and every one of them it’s really time consuming - short summary is not  
enought

Documentation itself is good - true, but it took me few hours of reading  
your blog, wikipedia and source code to understand what was basic  
concept and how i could use it to make my idea work 🙂

not to mention that someone without solid c background and idea how ruby  
internals work won’t be able to understand jack.  
I finally got the grasp when i stared inspecting Ruby2Ruby.

and bugs that I reported for Ruby2C were never even acknowledged 🙂

Aside from that this stuff is really powerfull, and having it when  
working on FreeRIDE coloring and code completion (which i never  
finished) would be awesome.

My idea of transfering ruby code beetween procesing nodes might come  
true. And i would like to really thank you for that 🙂

greets

---

<div class="post-metadata">

**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [January 6, 2008, 12:34am UTC](https://www.ruby-forum.com/t/fwd-parse-tree-redux/125066/6 "2008-01-06T00:34:54Z")

</div>

> I still don’t understand the 1-line obsession… and yes, that is  
> naive, it’ll break on strings, sub-procs, pretty much all blocks, etc.  
> You can’t treat “statements” in ruby as each line of a block. #to\_ruby  
> is probably not what you want.

Unfortunately I think that’s true. What I need to do basically (I  
think) is just rewrite the stuff that generates the code.

–  
Giles B.

Podcast: [http://hollywoodgrit.blogspot.com](http://hollywoodgrit.blogspot.com)  
Blog: [http://gilesbowkett.blogspot.com](http://gilesbowkett.blogspot.com)  
Portfolio: [http://www.gilesgoatboy.org](http://www.gilesgoatboy.org)  
Tumblelog: [http://giles.tumblr.com](http://giles.tumblr.com)