Functions for data types

• FormatType
• ParseType
• TypeOf
• InstanceOf
• DataType
• OptionalType
• ListType and StreamType
• DictType
• TupleType
• StructType
• VariantType
• ResourceType
• CallableType
• GenericType, UnitType, and VoidType
• OptionalItemType, ListItemType and StreamItemType
• DictKeyType and DictPayloadType
• TupleElementType
• StructMemberType
• CallableResultType and CallableArgumentType
• VariantUnderlyingType

FormatType

Serializing a type to a human-readable string. This helps at debugging and will also be used in the next examples of this section. Documentation for the format.

ParseType

Building a type from a string with description. Documentation for its format.

Examples

SELECT FormatType(ParseType("List<Int32>"));  -- List<int32>

TypeOf

Getting the type of value passed to the argument.

Examples

SELECT FormatType(TypeOf("foo"));  -- String

SELECT FormatType(TypeOf(AsTuple(1, 1u))); -- Tuple<Int32,Uint32>

InstanceOf

Returns an instance of the specified type that can only be used to get the type of the result of an expression that uses this type.

If this instance remains in the computation graph by the end of optimization, the operation fails.

Examples

SELECT FormatType(TypeOf(
    InstanceOf(ParseType("Int32")) +
    InstanceOf(ParseType("Double"))
)); -- Double, because "Int32 + Double" returns Double

DataType

Returns a type for primitive data types based on type name.

Examples

SELECT FormatType(DataType("Bool")); -- Bool
SELECT FormatType(DataType("Decimal","5","1")); -- Decimal(5,1)

OptionalType

Adds the option to assign NULL to the passed type.

Examples

SELECT FormatType(OptionalType(DataType("Bool"))); -- Bool?

ListType and StreamType

Builds a list type or stream type based on the passed element type.

Examples

SELECT FormatType(ListType(DataType("Bool"))); -- List<Bool>

DictType

Builds a dictionary type based on the passed key types (first argument) and value types (second argument).

Examples

SELECT FormatType(DictType(
    DataType("String"),
    DataType("Double")
)); -- Dict<String,Double>

TupleType

Builds the tuple type from the passed element types.

Examples

SELECT FormatType(TupleType(
    DataType("String"),
    DataType("Double"),
    OptionalType(DataType("Bool"))
)); -- Tuple<String,Double,Bool?>

StructType

Builds the structure type based on the passed element types. The standard syntax of named arguments is used to specify the element names.

Examples

SELECT FormatType(StructType(
    DataType("Bool") AS MyBool,
    ListType(DataType("String")) AS StringList
)); -- Struct<'MyBool':Bool,'StringList':List<String>>

VariantType

Returns the type of a variant based on the underlying type (structure or tuple).

Examples

SELECT FormatType(VariantType(
  ParseType("Struct<foo:Int32,bar:Double>")
)); -- Variant<'bar':Double,'foo':Int32>

ResourceType

Returns the type of the resource based on the passed string label.

Examples

SELECT FormatType(ResourceType("Foo")); -- Resource<'Foo'>

CallableType

Constructs the type of the called value using the following arguments:

1. Number of optional arguments (if all arguments are required — 0).
2. Result type.
3. All the next arguments of CallableType are treated as types of arguments of the callable value, but with a shift for two required arguments (for example, the third argument of the CallableType describes the type of the first argument in the callable value).

Examples

SELECT FormatType(CallableType(
  1, -- optional args count
  DataType("Double"), -- result type
  DataType("String"), -- arg #1 type
  OptionalType(DataType("Int64")) -- arg #2 type
)); -- Callable<(String,[Int64?])->Double>

GenericType, UnitType, and VoidType

Return the same-name special data types. They have no arguments because they are not parameterized.

Examples

SELECT FormatType(VoidType()); -- Void

OptionalItemType, ListItemType and StreamItemType

Perform the action reverse to OptionalType, ListType, and StreamType: return the item type based on its container type.

Examples

SELECT FormatType(ListItemType(
  ParseType("List<Int32>")
)); -- Int32

DictKeyType and DictPayloadType

Returns the type of the key or value based on the dictionary type.

Examples

SELECT FormatType(DictKeyType(
  ParseType("Dict<Int32,String>")
)); -- Int32

TupleElementType

Returns the tuple’s element type based on the tuple type and the element index (index starts from zero).

Examples

SELECT FormatType(TupleElementType(
  ParseType("Tuple<Int32,Double>"), "1"
)); -- Double

StructMemberType

Returns the type of the structure element based on the structure type and element name.

Examples

SELECT FormatType(StructMemberType(
  ParseType("Struct<foo:Int32,bar:Double>"), "foo"
)); -- Int32

CallableResultType and CallableArgumentType

CallableResultType returns the result type based on the type of the called value. CallableArgumentType returns the argument type based on the called value type and its index (index starts from zero).

Examples

$callable_type = ParseType("(String,Bool)->Double");
SELECT FormatType(CallableResultType(
    $callable_type
)), -- Double
FormatType(CallableArgumentType(
    $callable_type, 1
)); -- Bool

VariantUnderlyingType

Performs an action reverse to VariantType: it returns the underlying type based on the variant type.

Examples

SELECT FormatType(VariantUnderlyingType(
  ParseType("Variant<foo:Int32,bar:Double>")
)), -- Struct<'bar':Double,'foo':Int32>
FormatType(VariantUnderlyingType(
  ParseType("Variant<Int32,Double>")
)); -- Tuple<Int32,Double>