Regular expressions and conditionals


#1

I’m writting a little program to convert some source files to html.

I’m using regexp’s to determine the content of each line and format it
accordingly. For example, if the line starts with a #, then it should be
output with a div (and id set to ‘comment’).

The problem is with matching the regular expressions. If I do this:

f = File.new(“myfile”, “r”)
while !f.eof?
line = f.gets

if line.match(/^# (.)/)
puts "

#{line.match(/^# (.)/)[0]}
"
end
end

Then not only do I get the commen lines formatted properly, I also get a
“nil” for every other line in the file.

How should I be using regexps in conditionals? I’m sure this should be
easy
but I’ve googled around for an hour and I can’t find what’s wrong.

TIA

Matt


#2

On 10/25/08, Matt H. removed_email_address@domain.invalid wrote:

line = f.gets

if line.match(/^# (.)/)
puts "

#{line.match(/^# (.)/)[0]}
"
end
end

I think what you’re trying to write is a little more like this:
f = File.new(“myfile”, “r”)
while line = f.gets
if line.match(/^# (.*)/)
line="

#{line.chomp}
\n"
end
puts line
end

Then not only do I get the commen lines formatted properly, I also get a
“nil” for every other line in the file.

I didn’t see any nils when I ran it… it just didn’t print anything
but comments. Which would be because your original only printed lines
back out if they matched your comment pattern.

Why do you have a space after the # in your pattern? I’ve found it to
be good luck to always escape # when in regexps, even if it isn’t
followed by a {. Probably a bug lurking in there.


#3

while line = f.gets
case line
when /^# (.)/
puts “

#{$1}

else
puts line
end
end

#4

On 26.10.2008 01:02, Caleb C. wrote:

while !f.eof?
while line = f.gets
if line.match(/^# (.*)/)
line="

#{line.chomp}
\n"
end
puts line
end

Even better is

Use the block form of File.open!

File.new(“myfile”, “r”) do |f|
f.each do |line|
line.chomp!
case line
when /^# (.)/
puts “

# {$1}

else
puts line
end
end
end

or, for that matter

File.foreach(“myfile”) do |line|
line.chomp!
case line
when /^# (.)/
puts “

# {$1}

else
puts line
end
end

Kind regards

robert