C alignment when printing cout

Question

Is there a way to align text when printing using std  cout  I m using tabs  but when the words are too big they won t be aligned anymore   Sales Report for September 15  2010 Artist  Title   Price   Genre   Disc    Sale    Tax Cash Merle   Blue    12 99   Country 4   12 47   1 01    13 48 Richard Music   8 49    Classical   8   7 81    0 66    8 47 Paula   Shut    8 49    Classical   8   7 81    0 72    8 49

User · Answer

Another way to make column aligned is as follows:

using namespace std;

cout.width(20); cout << left << "Artist";
cout.width(20); cout << left << "Title";
cout.width(10); cout << left << "Price";
...
cout.width(20); cout << left << artist;
cout.width(20); cout << left << title;
cout.width(10); cout << left << price;

We should estimate maximum length of values for each column. In this case, values of "Artist" column should not exceed 20 characters and so on.

User · Answer

C  20 std  format options  lt     and  gt  According to https   en cppreference com w cpp utility format formatter Standard format specification the following should hold     left   quot 42     quot  std  cout  lt  lt  std  format  quot    lt 6  quot   42       right   quot     42 quot  std  cout  lt  lt  std  format  quot    gt 6  quot   42       center   quot   42   quot  std  cout  lt  lt  std  format  quot    6  quot   42    More information at  std  string formatting like sprintf

User · Answer

At the time you emit the very first line   Artist  Title   Price   Genre   Disc    Sale    Tax Cash   to achieve  alignment   you have to know  in advance  how wide each column will need to be  otherwise  alignment is impossible    Once you do know the needed width for each column  there are several possible ways to achieve that depending on where your data s coming from   then the setw function mentioned in the other answer will help  or  more brutally -  you could emit carefully computed number of extra spaces  clunky  to be sure   etc  I don t recommend tabs anyway as you have no real control on how the final output device will render those  in general   Back to the core issue  if you have each column s value in a vector lt T gt  of some sort  for example  you can do a first formatting pass to determine the maximum width of the column  for example  be sure to take into account the width of the header for the column  too  of course    If your rows are coming  one by one   and alignment is crucial  you ll have to cache or buffer the rows as they come in  in memory if they fit  otherwise on a disk file that you ll later  rewind  and re-read from the start   taking care to keep updated the vector of  maximum widths of each column  as the rows do come   You can t output anything  not even the headers    if keeping alignment is crucial  until you ve seen the very last row  unless you somehow magically have previous knowledge of the columns  widths  of course -

User · Answer

The setw manipulator function will be of help here

User · Answer

The ISO C   standard way to do it is to  include  lt iomanip gt  and use io manipulators like std  setw  However  that said  those io manipulators are a real pain to use even for text  and are just about unusable for formatting numbers  I assume you want your dollar amounts to line up on the decimal  have the correct number of significant digits  etc    Even for just plain text labels  the code will look something like this for the first part of your first line      using standard iomanip facilities cout  lt  lt  setw 20   lt  lt   Artist        lt  lt  setw 20   lt  lt   Title        lt  lt  setw 8   lt  lt   Price          not going to try to write the numeric formatting      If you are able to use the Boost libraries  run  don t walk  and use the Boost Format library instead  It is fully compatible with the standard iostreams  and it gives you all the goodness for easy formatting with printf Posix formatting string  but without losing any of the power and convenience of iostreams themselves  For example  the first parts of your first two lines would look something like      using Boost Format cout  lt  lt  format   -20s  -20s  -8s n       Artist     Title     Price   cout  lt  lt  format   -20s  -20s  8 2f n      Merle     Blue    12 99

User · Answer

See also  Which C I O library should be used in C   code   struct Item      std  string     artist     std  string     c     integer         price      in cents  as floating point is not acurate     std  string     Genre     integer         disc     integer         sale     integer         tax      std  cout  lt  lt   Sales Report for September 15  2010 n             lt  lt   Artist  Title   Price   Genre   Disc    Sale    Tax Cash n   FOREACH Item loop data        fprintf stdout   8s 8s 8 2f 7s 1s 8 2f 8 2f n               loop artist             loop title             loop price   100 0             loop Genre             loop disc                   loop sale   100 0             loop tax   100 0          or      std  cout  lt  lt  std  setw 8   lt  lt  loop artist                lt  lt  std  setw 8   lt  lt  loop title                lt  lt  std  setw 8   lt  lt  fixed  lt  lt  setprecision 2   lt  lt  loop price   100 0                lt  lt  std  setw 8   lt  lt  loop Genre                lt  lt  std  setw 7   lt  lt  loop disc  lt  lt  std  setw 1   lt  lt                     lt  lt  std  setw 8   lt  lt  fixed  lt  lt  setprecision 2   lt  lt  loop sale   100 0                lt  lt  std  setw 8   lt  lt  fixed  lt  lt  setprecision 2   lt  lt  loop tax   100 0                lt  lt    n           or      std  cout  lt  lt  boost  format   8s 8s 8 2f 7s 1s 8 2f 8 2f n                   loop artist                 loop title                 loop price   100 0                 loop Genre                 loop disc                       loop sale   100 0                 loop tax   100 0

User · Answer

IO manipulators are what you need  setw  in particular  Here s an example from the reference page      setw example  include  lt iostream gt   include  lt iomanip gt  using namespace std   int main        cout  lt  lt  setw  10     cout  lt  lt  77  lt  lt  endl    return 0      Justifying the field to the left and right is done with the left and right manipulators   Also take a look at setfill  Here s a more complete tutorial on formatting C   output with io manipulators

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