Format output to 40 characters long per line

问题:

I'm fairly new to Ruby and I've been searching Google for a few hours now. Does anyone know how to format the output of a print to be no more than 40 characters long?

For example:

What I want to print:

This is a simple sentence.
This simple
sentence appears
on four lines. 

But I want it formatted as:

This is a simple sentence. This simple
sentence appears on four lines.

I have each line of the original put into an array.
so x = ["This is a simple sentence.", "This simple", "sentence appears", "on three lines."]
I tried x.each { |n| print n[0..40], " " } but it didn't seem to do anything.

Any help would be fantastic!

回答1:

The method word_wrap expects a Strind and makes a kind of pretty print.

Your array is converted to a string with join("\n")

The code:

def word_wrap(text, line_width = 40 ) 
  return text if line_width <= 0
  text.gsub(/\n/, ' ').gsub(/(.{1,#{line_width}})(\s+|$)/, "\\1\n").strip
end

x = ["This is a simple sentence.", "This simple", "sentence appears", "on three lines."]

puts word_wrap(x.join("\n"))
x << 'a' * 50 #To show what happens with long words
x << 'end'
puts word_wrap(x.join("\n"))

Code explanation:

x.join("\n")) build a string, then build one long line with text.gsub(/\n/, ' '). In this special case this two steps could be merged: x.join(" "))

And now the magic happens with

gsub(/(.{1,#{line_width}})(\s+|$)/, "\\1\n")

• (.{1,#{line_width}})): Take any character up to line_width characters.
• (\s+|$): The next character must be a space or line end (in other words: the previous match may be shorter the line_width if the last character is no space.
• "\\1\n": Take the up to 40 character long string and finish it with a newline.
• gsub repeat the wrapping until it is finished.

And in the end, I delete leading and trailing spaces with strip

I added also a long word (50 a's). What happens? The gsub does not match, the word keeps as it is.

回答2:

puts x.join(" ").scan(/(.{1,40})(?:\s|$)/m)

This is a simple sentence. This simple
sentence appears on three lines.

回答3:

Ruby 1.9 (and not overly efficient):

>> x.join(" ").each_char.each_slice(40).to_a.map(&:join)
=> ["This is a simple sentence. This simple s", "entence appears on three lines."]

The reason your solution doesn't work is that all the individual strings are shorter than 40 characters, so n[0..40] always is the entire string.