Info Catalog octave: Escape Sequences in String Constants octave: Strings octave: Creating Strings

octave: Character Arrays

 
 5.2 Character Arrays
 ====================
 
 The string representation used by Octave is an array of characters, so
 internally the string "dddddddddd" is actually a row vector of length 10
 containing the value 100 in all places (100 is the ASCII code of "d").
 This lends itself to the obvious generalization to character matrices.
 Using a matrix of characters, it is possible to represent a collection
 of same-length strings in one variable.  The convention used in Octave
 is that each row in a character matrix is a separate string, but letting
 each column represent a string is equally possible.
 
    The easiest way to create a character matrix is to put several
 strings together into a matrix.
 
      collection = [ "String #1"; "String #2" ];
 
 This creates a 2-by-9 character matrix.
 
    The function ‘ischar’ can be used to test if an object is a character
 matrix.
 
  -- : ischar (X)
      Return true if X is a character array.
 
DONTPRINTYET       See also: isfloat XREFisfloat, *noteisinteger:
DONTPRINTYET DONTPRINTYET       See also: isfloat XREFisfloat, isinteger

      XREFisinteger, islogical XREFislogical, *noteisnumeric:
DONTPRINTYET DONTPRINTYET       See also: isfloat XREFisfloat, isinteger

      XREFisinteger, islogical XREFislogical, isnumeric

      XREFisnumeric, iscellstr XREFiscellstr, isa XREFisa.
 
    To test if an object is a string (i.e., a character vector and not a
 character matrix) you can use the ‘ischar’ function in combination with
 the ‘isvector’ function as in the following example:
 
      ischar (collection)
           ⇒ 1
 
      ischar (collection) && isvector (collection)
           ⇒ 0
 
      ischar ("my string") && isvector ("my string")
           ⇒ 1
 
    One relevant question is, what happens when a character matrix is
 created from strings of different length.  The answer is that Octave
 puts blank characters at the end of strings shorter than the longest
 string.  It is possible to use a different character than the blank
 character using the ‘string_fill_char’ function.
 
  -- : VAL = string_fill_char ()
  -- : OLD_VAL = string_fill_char (NEW_VAL)
  -- : string_fill_char (NEW_VAL, "local")
      Query or set the internal variable used to pad all rows of a
      character matrix to the same length.
 
      The value must be a single character and the default is " " (a
      single space).  For example:
 
           string_fill_char ("X");
           [ "these"; "are"; "strings" ]
                 ⇒  "theseXX"
                     "areXXXX"
                     "strings"
 
      When called from inside a function with the "local" option, the
      variable is changed locally for the function and any subroutines it
      calls.  The original variable value is restored when exiting the
      function.
 
    This shows a problem with character matrices.  It simply isn’t
 possible to represent strings of different lengths.  The solution is to
 use a cell array of strings, which is described in Cell Arrays of
 Strings.
 

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