Character classification
A GLS locale groups the characters of a code set into character classes. Each class contains characters that have a related purpose.
The contents of a character class can be language specific. For example, the lower class contains all alphabetic lowercase characters in a code set. In the default locale, the default code set groups the English characters a through z into the lower class, but it also includes lowercase characters such as á, ⪚, , õ, and ü.
The default code set on UNIX platforms is ISO8859-1. The default code set for Windows environments is Microsoft 1252.
For more information about the default locale and the default code set, see the IBM® Informix GLS User's Guide.
The LC_CTYPE category of a GLS locale file defines the following
character classes.
| Character class | Contains |
|---|---|
| alpha | Alphabetic characters:
|
| lower | Lowercase alphabetic characters:
|
| upper | Uppercase alphabetic characters:
|
| digit | Single-byte decimal digits 0 through 9 |
| xdigit | Hexadecimal digits:
|
| alnum | All characters in both the alpha and digit classes. |
| blank | Horizontal white space:
|
| space | Horizontal and vertical white space:
|
| cntrl | Control characters:
|
| graph | Graphical characters are all characters that have visual representation. This class includes characters in the alpha, lower, upper, digit, xdigit, and punct classes. |
| punct | Punctuation:
|
| All printable characters This class includes characters in the alpha, lower, upper, digit, xdigit, graph, and punct classes. |
Your application must not assume which characters belong in a particular
character class. For example, it must not contain code such as the
following example to determine whether a character is lowercase:
if ( one_char >= 'a' && one_char <= 'z' )Instead, use functions in the HCL Informix® GLS library
to identify the class of a particular character. The following table
lists the GLS character classes and the Informix GLS functions
that test for these classes for both multibyte and wide characters.
| Character class | Multibyte-character function | Wide-character function |
|---|---|---|
| alnum (alpha or digit) | ifx_gl_ismalnum() | ifx_gl_iswalnum() |
| alpha | ifx_gl_ismalpha() | ifx_gl_iswalpha() |
| lower | ifx_gl_ismlower() | ifx_gl_iswlower() |
| upper | ifx_gl_ismupper() | ifx_gl_iswupper() |
| blank | ifx_gl_ismblank() | ifx_gl_iswblank() |
| space | ifx_gl_ismspace() | ifx_gl_iswspace() |
| digit | ifx_gl_ismdigit() | ifx_gl_iswdigit() |
| xdigit | ifx_gl_ismxdigit() | ifx_gl_iswxdigit() |
| cntrl | ifx_gl_ismcntrl() | ifx_gl_iswcntrl() |
| graph | ifx_gl_ismgraph() | ifx_gl_iswgraph() |
| punct | ifx_gl_ismpunct() | ifx_gl_iswpunct() |
| ifx_gl_ismprint() | ifx_gl_iswprint() |
These Informix GLS functions
check the LC_CTYPE category of the current locale to determine whether
a specified character belongs to the respective character classification.
The following code fragment uses the ifx_gl_ismlower() function
to determine whether a multibyte character is lowercase:
if ( ifx_gl_ismlower(one_char, char_size)The Informix GLS functions
in Table 1 do
not return a unique value if they encounter an error. To detect an
error, initialize the ifx_gl_lc_errno() error number
to 0 before you call one of these functions, and then call ifx_gl_lc_errno() immediately
after you call the function. For example, the following code fragment
performs error checking for the ifx_gl_ismlower() function:
/* Initialize the error number */
ifx_gl_lc_errno() = 0;
/* Determine if 'mb' character is lowercase */
value = ifx_gl_ismlower(mb, mb_size);
/* If the error number has changed, ifx_gl_ismlower()has
* set it to indicate the cause of an error */
if ( ifx_gl_lc_errno() != 0 )
/* Handle error */
else if ( value != 0 )
/* Character 'mb' is in lower class */
else if ( value == 0 )
/* Character 'mb' is NOT in lower class */