Parslet - Get Started typos

[tmcgilchrist]

Hi,

I just worked through the Get Started guide and noticed a few typos in the code. For example under the heading Making the parser complete

class MiniP < Parslet::Parser
  # Single character rules
  rule(:lparen)     { str('(') >> space? }
  rule(:rparen)     { str(')') >> space? }
  rule(:comma)      { str(',') >> space? }
  # etc
end

Looks like you need to escape the brackets to get it working.

Is there a copy of this page somewhere I could clone and provide a patch to fix theses issues?

[floere]

Hi Tim,

Thanks for the feedback. I can't seem to reproduce the problem, neither under 1.9.2 nor 1.8.7.

The quick example I used is:

require 'parslet'

class MiniP < Parslet::Parser
  # Single character rules
  rule(:lparen)     { str('(') >> space? }
  rule(:rparen)     { str(')') >> space? }
  rule(:comma)      { str(',') >> space? }

  rule(:space)      { match('\s').repeat(1) }
  rule(:space?)     { space.maybe }

  # Things
  rule(:integer)    { match('[0-9]').repeat(1).as(:int) >> space? }
  rule(:identifier) { match['a-z'].repeat(1) }
  rule(:operator)   { match('[+]') >> space? }

  # Grammar parts
  rule(:sum)        { integer.as(:left) >> operator.as(:op) >> expression.as(:right) }
  rule(:arglist)    { expression >> (comma >> expression).repeat }
  rule(:funcall)    { identifier.as(:funcall) >> lparen >> arglist.as(:arglist) >> rparen }

  rule(:expression) { funcall | sum | integer }
  root :expression
end

p MiniP.new.parse('puts(1 + 2)')

Cheers, Florian

[tmcgilchrist]

Hi Florian,

Yes indeed it does, my mistake sorry. I had my str('(') mixed up with match('(') thanks.

I was also a little confused about the full code listing at the bottom of the article.

class Addition < Struct.new(:left, :right) 
  def eval; left.eval + right.eval; end
end
class FunCall < Struct.new(:name, :args); 
  def eval
    p args.map { |s| s.eval }
  end
end

notice what appears to be a stray semi-colon at the end of the class FunCall. It doesn't break anything if you have it, and it still works if you remove it.

Is there a reason I'm missing for it to be there?

Cheers, Tim

[floere]

Hi Tim,

No worries.

My assumption is that Kaspar originally had the "class Funcall" thing on one line, using ; to help Ruby parse. And then, when formatting it, forgot to remove it. Or perhaps he had a flashback to his time as a Java (TM) programmer.

It isn't the most beautiful thing to look at, or necessary, but isn't a problem either.

So, in a nutshell: No, there is no important reason for it to be there, so don't be confused, please;

I'm closing this issue since all seems to be fine.

Cheers & thanks for using Parslet, Florian

[kschiess]

Thanks @floere for solving / answering this.

@tmcgilchrist: Thanks for joining and taking interest! If you find any real bugs in the documentation, you can check out the 'gh-pages' branch of parslet to correct the source. Hint: it's in the .source subdirectory of that branch.

[tmcgilchrist]

@floere @kschiess Thanks for the responses guys. I'll be sure to contribute anything back if I find real bugs. And thanks for the great library it's lots of fun to use.