0004.txt

来自「用ruby on rails写的一个博客程序,还不错..ruby on rail」· 文本 代码 · 共 32 行

Lexical analysis is performed by obtaining a tokenizer of the appropriate class and calling @tokenize@ on it, passing the text to be tokenized. Each token is yielded to the associated block as it is discovered.

{{{lang=ruby,number=true,caption=Tokenizing a Ruby script
require 'syntax'

tokenizer = Syntax.load "ruby"
tokenizer.tokenize( File.read( "program.rb" ) ) do |token|
  puts token
  puts "  group: #{token.group}"
  puts "  instruction: #{token.instruction}"
end
}}}

If you need finer control over the process, you can use the lower-level API:

{{{lang=ruby,number=true,caption=Tokenizing a Ruby script via step
require 'syntax'

tokenizer = Syntax.load "ruby"
tokenizer.start( File.read( "program.rb" ) ) do |token|
  puts token
  puts "  group: #{token.group}"
  puts "  instruction: #{token.instruction}"
end

tokenizer.step
tokenizer.step
...
tokenizer.finish
}}}

In this case, each time @#step@ is invoked, it results in tokens being consumed and yielded to the block. However, a single step may result in multiple tokens being detected and yielded--there is no way to guarantee a single token at a time, unless the corresponding syntax module was written to work that way. For efficiency, the existing modules will yield multiple tokens when processing (for instance) strings, regular expressions, and heredocs.