Using two justifications on the same line

Ruby
1

Ok, so the chapter I am working on now is asking for me to write a
table of contents with the title left justified and the pages right
justified. I did this much earlier in the book with individual lines,
and it came out fine. The code I used initially was :

line_width = 60
puts (“Chapter 1: Getting Started”.ljust(line_width/2) + “page
1”.rjust(line_width/2))
puts (“Chapter 2: Numbers”.ljust(line_width/2) + “page
9”.rjust(line_width/2))
puts (“Chapter 3: Letters”.ljust(line_width/2) + “page
13”.rjust(line_width/2))

The chapter I am reading now is about arrays, so I am supposed to load
the same data into an array and accomplish the same task. What Ive
tried is several variations on this:

chapters = [‘Chapter 1: Getting started’,‘Chapter 2: Numbers’,
‘Chapter 3: Letters’]
pages = [‘page 1’,‘page 9’, ‘page 13’]
line_width = 60
puts (chapters.ljust(line_width/2) + pages.rjust(line_width/2))

…with the last line having changed a number of times. Obviously, I
haven’t been able to get the code to run right. Could anyone tell me
what I am missing?

Shiloh

2

On Nov 20, 2006, at 6:07 PM, Shiloh M. wrote:

puts (“Chapter 3: Letters”.ljust(line_width/2) + “page 13”.rjust
puts (chapters.ljust(line_width/2) + pages.rjust(line_width/2))

…with the last line having changed a number of times. Obviously, I
haven’t been able to get the code to run right. Could anyone tell me
what I am missing?\

The problem is that an array doesn’t respond to either ljust or
rjust. You need to extract the strings from their containing arrays.
Also, it’s easier to use one array than two, so I recommend something
like:

source = [
‘Chapter 1: Getting started’,
‘page 1’,
‘Chapter 2: Numbers’,
‘page 9’,
‘Chapter 3: Letters’,
‘page 13’
]
line_width = 60
until source.empty?
chapter = source.shift
page = source.shift
puts chapter.ljust(line_width/2) + page.rjust(line_width/2)
end

Regards, Morton

3

Ok, I think i understand that…however the shift function hasn’t been
introduced yet. Is there another way that i COULD do it?

4

On Nov 21, 2006, at 7:00 AM, Shiloh M. wrote:

Ok, I think i understand that…however the shift function hasn’t been
introduced yet. Is there another way that i COULD do it?

Sure. In Ruby there are always many ways to achieve a goal. How about
this?

source = [
‘Chapter 1: Getting started’,
‘page 1’,
‘Chapter 2: Numbers’,
‘page 9’,
‘Chapter 3: Letters’,
‘page 13’
]
line_width = 60
i = 0
while i < source.length
chapter = source[i]
page = source[i+1]
puts chapter.ljust(line_width/2) + page.rjust(line_width/2)
i += 2
end

Regards, Morton

5

On 11/21/06, Shiloh M. [email protected] wrote:

Ok, I think i understand that…however the shift function hasn’t been
introduced yet. Is there another way that i COULD do it?

If you know the chapters and pages arrays are well-formed (that is,
they are the same size, and each page corresponds to the chapter in
the same position) you could do this:

chapters.each_with_index {|chapter, index|
page = pages[index]
…
}

martin

6

Shiloh M. wrote:

/ …

…with the last line having changed a number of times. Obviously, I
haven’t been able to get the code to run right. Could anyone tell me
what I am missing?

#!/usr/bin/ruby -w

chapter_list = [
“Getting Started|1”,
“Numbers|9”,
“Letters|13”
]

cn = 1

line_width = 60

lwd2 = line_width/2

chapter_list.each do |item|
chapter_name,page_number = item.split("|")
puts “Chapter #{cn}: #{chapter_name}”.ljust(lwd2) +
“#{page_number}”.rjust(lwd2)
cn += 1
end

Output:

Chapter 1: Getting Started 1
Chapter 2: Numbers 9
Chapter 3: Letters 13