Package software.amazon.smithy.rulesengine.language.syntax.expressions.functions

Class Coalesce

java.lang.Object

software.amazon.smithy.rulesengine.language.syntax.SyntaxElement

software.amazon.smithy.rulesengine.language.syntax.expressions.Expression

software.amazon.smithy.rulesengine.language.syntax.expressions.functions.LibraryFunction

software.amazon.smithy.rulesengine.language.syntax.expressions.functions.Coalesce

All Implemented Interfaces:

FromSourceLocation, ToNode, TypeCheck, ToCondition, ToExpression

public final class Coalesce
extends LibraryFunction

A coalesce function that returns the first non-empty value.

This variadic function requires two or more arguments. At runtime, returns the first argument that contains a non-EmptyValue, otherwise returns the result of the last argument.

Type checking rules:

• coalesce(T, T, T) => T (same types)
• coalesce(Optional<T>, T, T) => T (any non-optional makes result non-optional)
• coalesce(Optional<T>, Optional<T>, Optional<T>) => Optional<T> (all optional)

Available since: rules engine 1.1.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	Coalesce.Definition	A FunctionDefinition for the Coalesce function.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	ID

Fields inherited from class software.amazon.smithy.rulesengine.language.syntax.expressions.functions.LibraryFunction

definition, functionNode

Method Summary

Modifier and Type	Method	Description
<R> R	accept(ExpressionVisitor<R> visitor)	Invoke the ExpressionVisitor functions for this expression.
RulesVersion	availableSince()	Get the rules engine version that this syntax element is available since.
static Coalesce.Definition	getDefinition()	Gets the FunctionDefinition implementation.
static Coalesce	ofExpressions(List<? extends ToExpression> args)	Creates a Coalesce function from a list of expressions.
static Coalesce	ofExpressions(ToExpression... args)	Creates a Coalesce function from variadic expressions.
protected Type	typeCheckLocal(Scope<Type> scope)

Methods inherited from class software.amazon.smithy.rulesengine.language.syntax.expressions.functions.LibraryFunction

calculateReferences, canonicalize, equals, expectOneArgument, getArguments, getFunctionDefinition, getName, getSourceLocation, hashCode, shouldSwapArgs, toConditionBuilder, toNode, toString

Methods inherited from class software.amazon.smithy.rulesengine.language.syntax.expressions.Expression

fromNode, getLiteral, getReference, getReference, getReference, getReferences, of, of, of, parseShortform, toExpression, type, typeCheck

Methods inherited from class software.amazon.smithy.rulesengine.language.syntax.SyntaxElement

booleanEqual, getAttr, getAttr, isSet, isValidHostLabel, not, parseUrl, stringEqual, substring, template

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface software.amazon.smithy.rulesengine.language.syntax.ToCondition

toCondition, toCondition

Field Details

ID

public static final String ID

See Also:

• Constant Field Values

Method Details

getDefinition

public static Coalesce.Definition getDefinition()

Gets the FunctionDefinition implementation.

Returns:

the function definition.

ofExpressions

public static Coalesce ofExpressions(ToExpression... args)

Creates a Coalesce function from variadic expressions.

Parameters:

args - the expressions to coalesce

Returns:

The resulting Coalesce function.

ofExpressions

public static Coalesce ofExpressions(List<? extends ToExpression> args)

Creates a Coalesce function from a list of expressions.

Parameters:

args - the expressions to coalesce

Returns:

The resulting Coalesce function.

availableSince

public RulesVersion availableSince()

Description copied from class: SyntaxElement

Get the rules engine version that this syntax element is available since.

Overrides:

availableSince in class SyntaxElement

Returns:

the version this is available since.

accept

public <R> R accept(ExpressionVisitor<R> visitor)

Description copied from class: Expression

Invoke the ExpressionVisitor functions for this expression.

Specified by:

accept in class Expression

Type Parameters:

R - the visitor return type.

Parameters:

visitor - the visitor to be invoked.

Returns:

the return value of the visitor.

typeCheckLocal

protected Type typeCheckLocal(Scope<Type> scope)
                       throws InnerParseError

Overrides:

typeCheckLocal in class LibraryFunction

Throws:

InnerParseError