意外的正则表达式行为

Question

When running the following piece of code in ruby:

string = "\begin{theorem}[blaat] \label{thm:foo}"
pattern = /^\\begin\{(theorem|definition)\}(\[.+\])?\s\\label\{(thm|def):.+\}$/
if string =~ pattern then
    puts "match"    
else
    puts "no match"
end

I get a "no match" output.

However, when using the same pattern and string on rubular I get a match. The irregularities already start when using the above code with pattern:

/^\\begin/

and string \begin . This does not match using the above snippet, but it does on rubular.com

I'm using Ruby 1.9.1

Answer 1

The problem is with your input string. You have a backspace character "\b" . Try using a single-quoted string instead:

string = '\begin{theorem}[blaat] \label{thm:foo}'