String operators (+, CONCAT)
String operators are operators which parameters and result are the properties which values are instances of the string classes. The platform currently supports the following string operators:
| Operator | Name | Description | Example | Result |
|---|---|---|---|---|
+, CONCAT | Concatenation | Returns a string obtained by concatenating the operand strings | 'a' + 'b' | 'ab' |
The + operator returns NULL if one of the operands is NULL. The CONCAT operator treats a NULL operand as an empty string (however, concatenating values that are all NULL still returns NULL) and joins the operands with a delimiter that is inserted only between operands that are not NULL. For example, CONCAT ' ', 'John', 'Smith' = 'John Smith', but CONCAT ' ', 'John', NULL = 'John'.
Result class
The result class is defined as:
| Operator | Description |
|---|---|
+, CONCAT | result = STRING[p1.blankPadded AND p2.blankPadded, p1.caseInsensitive OR p2.caseInsensitive, p1.length + p2.length] |
where blankPadded, caseInsensitive and length are determined similarly to the rules for construction of a common ancestor for two built-in classes (Strings family). For CONCAT, the result length also includes the delimiter inserted between operands.
In the + and CONCAT operators, operands whose classes are other than string are cast to strings in accordance with the following table:
| Class | Cast class |
|---|---|
DATE, DATETIME, ZDATETIME, TIME | STRING[25] |
NUMERIC | STRING[p.length] |
INTEGER, YEAR | STRING[11] |
LONG, DOUBLE | STRING[20] |
BOOLEAN, TBOOLEAN | STRING[1] |
FILE, NAMEDFILE, files of a specific type, file links, HTML | STRING (unlimited length) |
| Object | STRING[20] |
| Other | STRING[8] |
If any operand belongs to the unlimited-length string class TEXT (or to one of its variants such as rich or HTML text), the result is that text class rather than a fixed-length string. For + with several such operands, RICHTEXT takes precedence over HTMLTEXT, and both over TEXT. For CONCAT, the last operand of the TEXT, RICHTEXT, HTMLTEXT, JSON or JSONTEXT class determines the result class: JSON and JSONTEXT give TEXT. Otherwise, the result has the class of that operand.
Language
The summation operator concatenates strings when at least one operand is a string — see the arithmetic operators. Its bracketed form, which treats NULL as 0, does not concatenate strings: it is defined for numeric classes only.
To concatenate several values with a delimiter inserted only between operands that are not NULL, use the CONCAT operator.
Examples
CLASS Person;
firstName = DATA STRING[100] (Person);
middleName = DATA STRING[100] (Person);
lastName = DATA STRING[100] (Person);
// if some part of the name is not specified, then this part will be skipped along with a space
fullName(Person p) = CONCAT ' ', firstName(p), middleName(p), lastName(p);