org.millscript.millscript.expr
Class CheckNoneExpr

java.lang.Object
  org.millscript.millscript.expr.Expr<CheckNoneAction>
      org.millscript.millscript.expr.CheckNoneExpr

All Implemented Interfaces:

ZeroResults

public final class CheckNoneExpr
extends Expr<CheckNoneAction>
implements ZeroResults

This class implements a check none expression. A check none expression is guaranteed to return no results.

See Also:

CheckNoneAction

Constructor Summary

CheckNoneExpr(Expr<?> x)
Creates a new check none expression, to check the specified expression returns no results.

Method Summary

CheckNoneAction	compileIt() Compiles this expression into an action.
static Expr<?>	make(Expr<?> x) Returns an expression that is guaranteed to return no results.
void	resolve(CompilerState state) Resolves any NameExpr in the tree so that they refer to the correct ident.

Methods inherited from class org.millscript.millscript.expr.Expr

arity, compile, isIntegerExpr, resolveList, setLineNumber, setOrigin, show, show

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CheckNoneExpr

public CheckNoneExpr(Expr<?> x)

Creates a new check none expression, to check the specified expression returns no results.

Parameters:

x - the expression which must return no results

Method Detail

make

public static Expr<?> make(Expr<?> x)

Returns an expression that is guaranteed to return no results. This method provides some compile-time optimisation, as it avoids creating additional unnecessary objects in the expression tree. If the specified expression already returns no results, it is simply returned, otherwise if it returns an unknown number of results, a new check none expression is created.

Parameters:

x - the expression which must return no results

Returns:

the specified expression if it already returns no results, otherwise a new CheckNoneExpr

compileIt

public CheckNoneAction compileIt()

Description copied from class: Expr

Compiles this expression into an action.

Specified by:

compileIt in class Expr<CheckNoneAction>

Returns:

the Action for this expression

See Also:

Expr.compileIt()

resolve

public void resolve(CompilerState state)

Description copied from class: Expr

Resolves any NameExpr in the tree so that they refer to the correct ident. e.g. This method is responsible for ensuring that references to a function argument in the body of a function actually refer to the correct value.

Specified by:

resolve in class Expr<CheckNoneAction>

Parameters:

state - the compiler state we are resolving in

See Also:

Expr.resolve(org.millscript.millscript.vm.CompilerState)