octave: Concatenating Strings
5.3.1 Concatenating Strings
---------------------------
Strings can be concatenated using matrix notation (
Strings,
Character Arrays) which is often the most natural method. For
example:
fullname = [fname ".txt"];
email = ["<" user "@" domain ">"];
In each case it is easy to see what the final string will look like.
This method is also the most efficient. When using matrix concatenation
the parser immediately begins joining the strings without having to
process the overhead of a function call and the input validation of the
associated function.
Nevertheless, there are several other functions for concatenating
string objects which can be useful in specific circumstances: ‘char’,
‘strvcat’, ‘strcat’, and ‘cstrcat’. Finally, the general purpose
DONTPRINTYET concatenation functions can be used: see cat XREFcat, *noteDONTPRINTYET concatenation functions can be used: see cat XREFcat,
horzcat XREFhorzcat, and vertcat XREFvertcat.
• 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])
⇒ banana
• ‘char’ and ‘strvcat’ concatenate vertically, while ‘strcat’ and
‘cstrcat’ concatenate horizontally. For example:
char ("an apple", "two pears")
⇒ an apple
two pears
strcat ("oc", "tave", " is", " good", " for you")
⇒ 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")
⇒ orange
green
red
strvcat ("orange", "green", "", "red")
⇒ orange
green
red
• All string concatenation functions except ‘cstrcat’ also accept
cell array data (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"})
⇒ red
green
blue
strcat ({"abc"; "ghi"}, {"def"; "jkl"})
⇒
{
[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"])
⇒ dir1/file1
directory2/file2
cstrcat (["thirteen apples"; "a banana"], [" 5$";" 1$"])
⇒ 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 (Character Arrays).
-- : char (X)
-- : char (X, ...)
-- : char (S1, S2, ...)
-- : 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 XREFstrvcat, cellstr XREFcellstr.
-- : strvcat (X)
-- : strvcat (X, ...)
-- : strvcat (S1, S2, ...)
-- : 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"]
DONTPRINTYET See also: char XREFchar, strcat XREFstrcat, *noteDONTPRINTYET See also: char XREFchar, strcat XREFstrcat,
cstrcat XREFcstrcat.
-- : strcat (S1, S2, ...)
Return a string containing all the arguments concatenated
horizontally.
If the arguments are cell 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 for any character string input is eliminated
before the strings are concatenated. Note that cell string values
do *not* have whitespace trimmed.
For example:
strcat ("|", " leading space is preserved", "|")
⇒ | leading space is preserved|
strcat ("|", "trailing space is eliminated ", "|")
⇒ |trailing space is eliminated|
strcat ("homogeneous space |", " ", "| is also eliminated")
⇒ homogeneous space || is also eliminated
s = [ "ab"; "cde" ];
strcat (s, s, s)
⇒
"ababab "
"cdecdecde"
s = { "ab"; "cd " };
strcat (s, s, s)
⇒
{
[1,1] = ababab
[2,1] = cd cd cd
}
DONTPRINTYET See also: cstrcat XREFcstrcat, char XREFchar, *noteDONTPRINTYET See also: cstrcat XREFcstrcat, char XREFchar,
strvcat XREFstrvcat.
-- : cstrcat (S1, S2, ...)
Return a string containing all the arguments concatenated
horizontally with trailing white space preserved.
For example:
cstrcat ("ab ", "cd")
⇒ "ab cd"
s = [ "ab"; "cde" ];
cstrcat (s, s, s)
⇒ "ab ab ab "
"cdecdecde"
DONTPRINTYET See also: strcat XREFstrcat, char XREFchar, *noteDONTPRINTYET See also: strcat XREFstrcat, char XREFchar,
strvcat XREFstrvcat.
Info Catalog
octave: Creating Strings
octave: Converting Numerical Data to Strings