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## jif.types
Class LabelSubstitution

    java.lang.Object
      jif.types.LabelSubstitution

Direct Known Subclasses:
  JifFieldDeclExt_c.InvarianceLabelChecker, JifFieldDeclExt_c.StaticFieldLabelChecker, JifSubst_c.SubstLabelSubst, JifTypeNodeDel.StaticLabelChecker

    public abstract class LabelSubstitution

extends java.lang.Object

The class is a simple Label visitor. It can be used to substitute and check labels and principals. All labels and principals implement a method `subst(LabelSubstitution)`.

In addition, the LabelSubstitution keeps a stack of labels, to record which labels it is in the middle of processing. Labels that recurse on nested labels must push themselves onto the stack before the recursive call, and pop themselves off the stack after the recursive call. Prior to pushing themselves on the stack, labels should examine the stack to see if they already exist in the stack; if so, then the label should not make a recursive call, in order to avoid an infinite loop.

See Also:
  `Label.subst(LabelSubstitution)`

Constructor Summary
`LabelSubstitution()`

Method Summary
`void` | `popLabel(Label l)`
`void` | `pushLabel(Label l)`
`boolean` | `stackContains(Label l)`
`Label` | `substLabel(Label L)`
`Principal` | `substPrincipal(Principal p)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### LabelSubstitution

    public LabelSubstitution()

Method Detail

### substLabel

    public Label substLabel(Label L)
                     throws polyglot.types.SemanticException

  Throws:
    `polyglot.types.SemanticException`

### substPrincipal

    public Principal substPrincipal(Principal p)
                             throws polyglot.types.SemanticException

  Throws:
    `polyglot.types.SemanticException`

### pushLabel

    public void pushLabel(Label l)

### popLabel

    public void popLabel(Label l)

### stackContains

    public boolean stackContains(Label l)

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