Concatenating Strings - GNU Octave
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#### 5.3.1 Concatenating Strings

It has been shown above that strings can be concatenated using matrix notation (see Strings, Character Arrays). Apart from that, there are several functions to concatenate string objects: `char`, `strvcat`, `strcat` and `cstrcat`. In addition, the general purpose concatenation functions can be used: see cat, horzcat and vertcat.

- All string concatenation functions except `cstrcat` convert numerical input into character data by taking the corresponding ASCII character for each element, as in the following example:

                char([98, 97, 110, 97, 110, 97])
                     ⇒ ans =
                       banana

- `char` and `strvcat` concatenate vertically, while `strcat` and `cstrcat` concatenate horizontally. For example:

                char("an apple", "two pears")
                     ⇒ ans =
                       an apple
                       two pears

                strcat("oc", "tave", " is", " good", " for you")
                     ⇒ ans =
                       octave is good for you

- `char` generates an empty row in the output for each empty string in the input. `strvcat`, on the other hand, eliminates empty strings.

                char("orange", "green", "", "red")
                     ⇒ ans =
                       orange
                       green

                       red

                strvcat("orange", "green", "", "red")
                     ⇒ ans =
                       orange
                       green
                       red

- All string concatenation functions except `cstrcat` also accept cell array data (see Cell Arrays). `char` and `strvcat` convert cell arrays into character arrays, while `strcat` concatenates within the cells of the cell arrays:

                char({"red", "green", "", "blue"})
                     ⇒ ans =
                       red
                       green

                       blue

                strcat({"abc"; "ghi"}, {"def"; "jkl"})
                     ⇒ ans =
                       {
                         [1,1] = abcdef
                         [2,1] = ghijkl
                       }

- `strcat` removes trailing white space in the arguments (except within cell arrays), while `cstrcat` leaves white space untouched. Both kinds of behavior can be useful as can be seen in the examples:

                strcat(["dir1";"directory2"], ["/";"/"], ["file1";"file2"])
                     ⇒ ans =
                       dir1/file1
                       directory2/file2

                cstrcat(["thirteen apples"; "a banana"], [" 5$";" 1$"])
                     ⇒ ans =
                       thirteen apples 5$
                       a banana        1$

  Note that in the above example for `cstrcat`, the white space originates from the internal representation of the strings in a string array (see Character Arrays).

— Built-in Function: char (x)
— Built-in Function: char (x, ...)
— Built-in Function: char (s1, s2, ...)
— Built-in Function: char (cell_array)

> Create a string array from one or more numeric matrices, character matrices, or cell arrays. Arguments are concatenated vertically. The returned values are padded with blanks as needed to make each row of the string array have the same length. Empty input strings are significant and will concatenated in the output.

> For numerical input, each element is converted to the corresponding ASCII character. A range error results if an input is outside the ASCII range (0-255).

> For cell arrays, each element is concatenated separately. Cell arrays converted through `char` can mostly be converted back with `cellstr`. For example:

>               char ([97, 98, 99], "", {"98", "99", 100}, "str1", ["ha", "lf"])
>                    ⇒ ["abc    "
>                        "       "
>                        "98     "
>                        "99     "
>                        "d      "
>                        "str1   "
>                        "half   "]

> See also: strvcat, cellstr.

— Built-in Function: strvcat (x)
— Built-in Function: strvcat (x, ...)
— Built-in Function: strvcat (s1, s2, ...)
— Built-in Function: strvcat (cell_array)

> Create a character array from one or more numeric matrices, character matrices, or cell arrays. Arguments are concatenated vertically. The returned values are padded with blanks as needed to make each row of the string array have the same length. Unlike `char`, empty strings are removed and will not appear in the output.

> For numerical input, each element is converted to the corresponding ASCII character. A range error results if an input is outside the ASCII range (0-255).

> For cell arrays, each element is concatenated separately. Cell arrays converted through `strvcat` can mostly be converted back with `cellstr`. For example:

>               strvcat ([97, 98, 99], "", {"98", "99", 100}, "str1", ["ha", "lf"])
>                    ⇒ ["abc    "
>                        "98     "
>                        "99     "
>                        "d      "
>                        "str1   "
>                        "half   "]

> See also: char, strcat, cstrcat.

— Function File: strcat (s1, s2, ...)

> Return a string containing all the arguments concatenated horizontally. If the arguments are cells strings, `strcat` returns a cell string with the individual cells concatenated. For numerical input, each element is converted to the corresponding ASCII character. Trailing white space is eliminated. For example:

>               s = [ "ab"; "cde" ];
>               strcat (s, s, s)
>                    ⇒ ans =
>                       "ab ab ab "
>                       "cdecdecde"

>               s = { "ab"; "cde" };
>               strcat (s, s, s)
>                    ⇒ ans =
>                       {
>                         [1,1] = ababab
>                         [2,1] = cdecdecde
>                       }

> See also: cstrcat, char, strvcat.

— Function File: cstrcat (s1, s2, ...)

> Return a string containing all the arguments concatenated horizontally. Trailing white space is preserved. For example:

>               cstrcat ("ab   ", "cd")
>                    ⇒ "ab   cd"

>               s = [ "ab"; "cde" ];
>               cstrcat (s, s, s)
>                    ⇒ ans =
>                       "ab ab ab "
>                       "cdecdecde"

> See also: strcat, char, strvcat.