Data types

Scalar types#

Every value in a script carries a concrete type. The type names below are used in typed declarations (see Local variables), and the .Type property returns them.

Int32 x := 4; fails with Unknown variable or constant 'Int32'. Names such as Int32 and UInt32 exist only among the Modbus data types of MODBUSR and MODBUSW.

Structured types#

Structured types hold several values, available as properties:

Enum types#

An enum type is a fixed set of named values that some functions take as a parameter:

An enum value is written bare (Utc) or with its type (DateTimeKind.Utc). Enum types also work as declaration keywords:

DateTimeKind kind := Utc;
VAR t := NOW(kind);

Collections#

collection<T> is a list of values of one element type T.

collection<uint16> registers := UINT16COLLECTION(4);
collection<string> names := {"a", "b", "c"};
collection<uint8> data := BYTECOLLECTION("0A0B0C");
LENGTH(names);
# Result: 3

• The element type comes from the declaration, otherwise from the first element that is not Null. {Null} alone fails with Unable to determine collection type.
• Nested collections are not supported: Collection<Collection<>> is not supported.
• Collections are reference values. APPEND, INSERT, REMOVEAT, SETAT and REPLACE change the collection in place and return the same collection.
• BYTECOLLECTION, UINT16COLLECTION and BOOLCOLLECTION create at most 2048 elements; each form reports a larger count with its own message (see Run-time errors).
• LENGTH(c) or c.Length returns the number of elements.

Available — typed collections from Core 2022.2; UINT16COLLECTION and BOOLCOLLECTION from Core 2026.1, build 39001.

The .Type property#

Every value has the read-only property .Type, which returns the name of its type as text. For an enum value it is the enum type, for example "DateTimeKind".

VAR x := 5.5;
x.Type;
# Result: "Double"
VAR c := BYTECOLLECTION("0A0B");
c.Type;
# Result: "Collection<UInt8>"

Properties can be read only from a named variable. AVG('a', 'c').Type fails with Unexpected character '.'; store the value in a variable first.

Type conversion rules#

In arithmetic the first rule that matches the two operands decides the type of the result:

1. Either operand is double (or a group value): double.
2. Either operand is float: float.
3. Either operand is int64: int64.
4. Either operand is uint64: uint64.
5. Either operand is uint: uint when the other one is unsigned too, otherwise int64.
6. Otherwise (smaller integers, bool, char): int.

Division of two integers truncates. A number literal is a double, so dividing by it does not:

int a := 5;
int b := 2;
a / b;
# Result: 2
a / 2;
# Result: 2.5

• Bitwise operators work on integers; a double operand is converted to int64 first.
• + with a string on either side joins text: "T=" + 21.5 is "T=21.5".
• datetime + number adds milliseconds, datetime + timespan adds the interval, and timespan ± timespan works as expected.
• Dividing by zero stops the script with Division by zero. Guard the divisor with IF.
• Assigning to a typed variable converts the value to its type, see Local variables.

Null and NaN#

NaN is a number whose value is unknown, for example a sensor that was not read yet or a device in error. Null means there is no value at all: a deleted device, or a function that found nothing.

• Comparing with the literal NaN (x = NaN, x < NaN) is rejected when the script is parsed: Comparison with NaN is always false. Use the IsNaN method to check for NaN value. Use ISNAN.
• <, >, <= and >= with a Null operand give FALSE. Null = Null, Null <= Null and Null >= Null are TRUE, Null = 5 is FALSE.
• &, | and ^ with a Null operand give Null; << and >> give Null for a Null value on the left, while a Null shift count stops the script with Cannot cast DataType.Null to number.
• Arithmetic and logic with Null (Null + 5, !Null) stops the script with Operator '+' not defined for 'Null' and 'Double'. Check the value with ISNULL first.
• A Null condition of IF counts as FALSE.
• MIN, MAX, AVG and ORDER skip Null and NaN; the …STRICT variants pass them on. EQUALS(NaN, NaN) is TRUE.

IF(ISNULL(value) OR ISNAN(value), 0, value);
# Result: the value, or 0 when it is missing or unknown