Syntax Strings for Pattern Matching
Uniface enables you to determine if the data in a string value matches a desired
pattern using syntax strings. A syntax string is a group of characters and syntax codes
(#, *, &, @,
~, ?, (, ), %,
and ^) enclosed in single quotation marks (').
Syntax strings can be used to specifying a field syntax, such as postal code or telephone number. They are also useful when searching for and comparing or replacing strings. For example, they can be used when:
- Defining logical expressions with the
=,==, and!=operators in conditional ProcScript statements (if, repeat, selectcase, or while).Note: In a logical expression, the pattern specified by the syntax string must occur within the first 256 characters of the string with which it is being compared.
- Searching and replacing strings using scan, $scan, $rscan, $replace.
- Truncating strings using $ltrim and $rtrim
Using Syntax Strings
To represent the pattern of a Canadian postal code
(such as B2Y 5K2), the syntax string would be &#& #&#, where the
syntax code # represents a number and & a letter.
To enforce this pattern in a data entry field, you can specify this syntax string in the Field Syntax property.
In ProcScript, you can use $syntax to convert a string to a syntax string, and use this to search for a matching string. For example:
;Field ADDRESS = "Mary John, 2 Ginger Lane, Genoa NS B0R 1N6" ; Scan the string for a substring that matches the postal code pattern, ; and return the position of the matching string vLocation = $scan (ADDRESS, $syntax(&#& #&#)) ; If a position is returned, issue a message if (vLocation > 0) putmess = "A postal code is provided" endif
Syntax of Syntax Strings
In ProcScript you can enter syntax strings using the correct syntax, or use the ProcScript function $syntax to convert a string to a syntax string.
Syntax:
'{[Mode]}PatternString{[ExitMode]}'
- Mode—syntax mode, which
determines how the subsequent characters will be handled. If omitted or set to
%[X]or%[Exit], the syntax characters (#,*,&,@,~,?,(,),%, and^) are interpreted and all other characters are treated as constants. If the Mode is set to any other value, all characters that follow are treated as constants, including the characters that are normally treated as syntax characters. - PatternString—string of
characters, which can include the following syntax codes:
#,*,&,@,~,?,(,),%, and^. - ExitMode—exit mode
%[X]or%[Exit], which turns off the mode that was previously set.
The maximum length of a syntax string is 127 characters.
Syntax Codes
| Syntax code | Explanation |
|---|---|
#
|
One digit (0-9) |
#*
|
0-n digits |
&
|
One letter (A-Z, a-z) |
&*
|
0-n letters |
@
|
One letter, digit, or underscore (_) |
@*
|
0-n letters, digits, or underscores |
Extended Characters. These are determined by the value of the $EXTENDED_SYNTAX assignment setting. Default is the full Unicode character set. For more information, see $EXTENDED_SYNTAX. |
|
~&
|
One extended letter. |
~&*
|
0-n extended letters |
~@
|
One extended letter, digit, or underscore (_) |
~@*
|
0-n characters, extended letters, digits, or underscores |
|
ASCII Characters |
|
?
|
One ASCII character |
?*
|
0-n ASCII characters |
A through Z |
That letter, in uppercase |
|
|
That letter, in uppercase or lowercase |
| x |
The
ASCII character x, except
the syntax codes (#, *, &, @, ~, ?, (, ), %, and ^)
|
%x
|
The ASCII character x, with no special meaning |
(any)
|
The syntax string (variable or constant) contained in parentheses is optional. A syntax check is done only if data is present. |
%%^ |
Carriage return or line feed.
Note: This code is allowed only to define entry formats in a field's syntax definition. It is not used in Proc pattern matching. |
To search for a character that is used as a syntax
code, you must set a syntax mode or precede it with a percent sign (%). Thus, to
search the literal percent sign, you can enter %%.
The fields and variables used in conjunction with
syntax strings must be data type string. If you need to use another type of data
(Numeric or Time, for example), first convert this to a string by substituting the value into a
constant string, for example "%%DATE1".
Syntax Modes
Syntax modes determine how characters and syntax codes are treated when performing a pattern-matching search.
| Syntax String Mode | Meaning | Example | Resulting Syntax String | Matches |
|---|---|---|---|---|
Classic
|
The following characters in
String are treated as syntax codes for pattern-matching: # * & @ ~ ? ( ) % ^This is the default, and corresponds to behavior prior to Uniface 9.4.01 |
$syntax("D&G") | '%[X]D&G' | DOG,
DIG, etc. |
CaseSensitive
|
Match only characters with the same case and treat syntax code characters as literals, not codes |
$syntax("D&G", "CS") |
'%[CS]D%&G%[X]' | D&G
|
CaseInSensitive
|
Match all characters irrespective of case,
and treat syntax code characters as literals, not codes Treat the characters that follow as case-insensitive. |
$syntax("D&G", "CI") |
'%[CI]D%&G%[X]' | D&G,
d&g, D&g, d&G |
NlsLocale
|
Match all characters irrespective of case according to the locale, and treat syntax code characters as literals, not codes |
$syntax("i#B", "NLS") |
'%[NLS]i%#B%[X]' | Depends on locale. If $NlsLocale |
The following ProcScript shows how a syntax string can be used in a conditional expression.
if (vValue = '#') message "%%vValue contains a digit." endif
The table contains shows the result of various
syntax strings, given that vValue = 123
|
ProcScript with Syntax String |
Result |
|---|---|
|
|
FALSE TRUE |
|
|
TRUE TRUE |
|
|
FALSE TRUE |
|
|
TRUE FALSE TRUE FALSE TRUE |
|
|
TRUE TRUE TRUE FALSE |
