View source for Talk:Align columns

== J solution ==

I haven't read the J solution in depth yet, but it appears more complex than may be necessary.  For example, with <code>'LEFT CENTER RIGHT'=:i.3</code> we can solve the task thus:

    _2 {:\ ": <;._2@:,~&>/'$';LF;text [ 9!:17 ,~ CENTER [ 9!:7 ' '$~11
    Given        a         text     file    of     many      lines,    where   fields  within    a    line  
     are     delineated     by       a    single 'dollar'  character,  write      a    program              
     that      aligns      each    column   of    fields       by     ensuring  that    words    in   each  
    column      are     separated    by     at     least      one      space.                               
   Further,    allow       for      each   word     in         a       column    to      be    either left  
  justified,   right    justified,   or   center justified   within     its    column.                      
                                                                                                            
Replacing <code>CENTER</code> with <code>LEFT</code> or <code>RIGHT</code> to taste. 

Now, of course, the justification selected applies to every word.  If we want to be able to treat each word (or column) independently, there are other methods.  Even for this more general specification, I'm still not convinced that the large explicit verb is required, but I'll have to review it in detail to confirm.

: I concur that your solution is adequate to the specified task. It should replace the one I posted. I wrote mine without knowing about 9!:y. Thank you for this more skillful solution, Dan. --[[User:TBH|TBH]] 22:58, 1 December 2008 (UTC)

: I've just noticed that the code proposed above does not compensate for the inconsistent input data, which lacks the delimiter at the end of some lines. (It does not seem right to me to have the example text have such an irregularity when nothing about the task suggests that data-quality testing is relevant, but, that's what we've been given.) --[[User:TBH|TBH]] 00:28, 2 December 2008 (UTC)

:: I have added a note to clarify that this aspect of the data is intentional. --[[User:Paddy3118|Paddy3118]] 03:52, 2 December 2008 (UTC)

:::  Fixed. --[[User:DanBron|DanBron]] 12:38, 2 December 2008 (UTC)

: The new solution has the column count hardcoded into it. I suspect that the task is intended to work such that the tally of columns is derived from the text, not provided by the user as part of the input. --[[User:TBH|TBH]] 22:34, 2 December 2008 (UTC)

:: Where is the column count hardcoded?  AFAIK, the number of columns wholly determined by the (maximum) number of <code>$</code>s in a line.  To be more explicit, the numeric constants are, from left to right: 
::{| class="wikitable" style="text-align: top,left; font-size: 85%; width: auto; table-layout: fixed;"
|-
| Constant
| Description
|-
| <code>'''_2''' {:\ ":</code>
| Non-overlapping (<code>'''-'''</code>) pairs (<code>'''2'''</code>) of rows of the formatted data.
|-
| <code><;.'''_2'''...</code>
| Split the input, treating the last (<code>'''2'''</code>) item as the fret, and exclude (<code>'''-'''</code>) the frets.
|-
| <code>'''9'''!:'''17'''</code>
| Foreign family controlling parameters (<code>'''9'''</code>), specifically controlling alignment (<code>'''17'''</code>).
|-
| <code>... ,~ '''CENTER''' ...</code>
| Parameter specifying centered alignment. (A prior version had <code>'''CENTER''' #~'''2'''</code>, which is the same, but one word longer)
|-
| <code>'''9'''!:'''7'''</code>
| Foreign family controlling parameters (<code>'''9'''</code>), specifically controlling linedrawing characters (<code>'''7'''</code>).
|-
| <code>' '$~'''11'''</code>
| Parameter specifying linedrawing characters (all <code>'''11'''</code> linedrawing characters will be <code>' '</code>).
|}
::--[[User:DanBron|DanBron]] 23:32, 2 December 2008 (UTC)

== Output Question ==
Given that the lines contain varying numbers of fields, when a justified line is output should the program<br \>
A) only output the justified fields that the line contains, or<br \>
B) output spaces for the columns when the line does not contain all the columns?

: Hi, assume that the output should look good visually, and that lines will never be wrapped when displayed so ''trailing'' whitespace is irrelevant. --[[User:Paddy3118|Paddy3118]] 03:39, 2 December 2008 (UTC)