org.erights.e.elang.evm
Class VarPattern

java.lang.Object
  |
  +--org.erights.e.elang.evm.ParseNode
        |
        +--org.erights.e.elang.evm.ENode
              |
              +--org.erights.e.elang.evm.Pattern
                    |
                    +--org.erights.e.elang.evm.NounPattern
                          |
                          +--org.erights.e.elang.evm.VarPattern

All Implemented Interfaces:

Cloneable, EPrintable, MatchMaker

public class VarPattern

extends NounPattern

Safe: BNF: 'var' ID ':' expr

The identifier on the left is the defining occurrence of a variable name. The expression on the right is a "slot guard expression". The object it evaluates to will be treated as a SlotGuard, and asked to make a slot initialized from a specimen, as if:

      def slot := slotGuard makeSlot(specimen, XXX)

 

This slot is then defined as the slot for a variable of this name in the scope starting immediately after this name.

But wait! That scope includes the slot guard expression?!? As with the def-expression, this circularity is indeed allowed and correct in the user-level language, but the kernel-level language (ie, the parse node VarPattern) imposes a well-formedness criterea that allows us to evaluate in the wrong order without effect. A circular user-level VarPattern is also statically rejected.

Author:

Mark S. Miller

See Also:

org.erights.e.elang.evm.DefineExpr, org.erights.e.elang.evm.FinalPattern

Field Summary

private EExpr

mySlotGuard

Fields inherited from class org.erights.e.elang.evm.NounPattern

Fields inherited from class org.erights.e.elang.evm.ENode

Fields inherited from class org.erights.e.elang.evm.ParseNode

NUM_PR, PR_ASSIGN, PR_CALL, PR_COMP, PR_EEXPR, PR_LISTPATT, PR_ORDER, PR_PATTERN, PR_PRIM, PR_START

Constructor Summary

VarPattern(SourceSpan optSpan, String varName, AtomicExpr noun, EExpr guardExpr)
Enabled: If 'varName' would shadow a non-shadowable, throw a (XXX to be defined) exception instead.

VarPattern(SourceSpan optSpan, String varName, EExpr guardExpr)
Enabled:

Method Summary

protected StaticScope	computeStaticScope() When staticScope() is first requested on a given node, it calls computeStaticScope() to do the actual computation, which is then remembered.
(package private) EExpr	guardExpr()
void	subPrintOn(TextWriter out, int priority) Enabled:
(package private) void	testMatch(EvalContext ctx, Object specimen, OneArgFunc optEjector) If this pattern matches the specimen, add macthing bindings to the scope.
Object	welcome(ETreeVisitor visitor) Enabled:

Methods inherited from class org.erights.e.elang.evm.NounPattern

ensureWellFormed, getNoun, matchBind, optName

Methods inherited from class org.erights.e.elang.evm.Pattern

__printOn, substitute

Methods inherited from class org.erights.e.elang.evm.ENode

cleanCopy, copy, getOptPatternMap, getOptScopeMap, getPatternMap, getScopeMap, qbuild, setPatternMap, setScopeMap, staticScope, synEnv

Methods inherited from class org.erights.e.elang.evm.ParseNode

asText, getOptSpan, lnPrintOn, lnPrintOn, matchBind, matchBind, matchBind, printListOn, toString

Methods inherited from class java.lang.Object

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

Field Detail

mySlotGuard

private final EExpr mySlotGuard

Constructor Detail

VarPattern

public VarPattern(SourceSpan optSpan,
                  String varName,
                  AtomicExpr noun,
                  EExpr guardExpr)

Enabled: If 'varName' would shadow a non-shadowable, throw a (XXX to be defined) exception instead.

If the VarPattern would not be well-formed, throw a (XXX to be defined) exception instead.

VarPattern

public VarPattern(SourceSpan optSpan,
                  String varName,
                  EExpr guardExpr)

Enabled:

Method Detail

welcome

public Object welcome(ETreeVisitor visitor)

Enabled:

Specified by:

welcome in class ENode

computeStaticScope

protected StaticScope computeStaticScope()

Description copied from class: ENode

When staticScope() is first requested on a given node, it calls computeStaticScope() to do the actual computation, which is then remembered.

Specified by:

computeStaticScope in class ENode

guardExpr

EExpr guardExpr()

Specified by:

guardExpr in class NounPattern

subPrintOn

public void subPrintOn(TextWriter out,
                       int priority)
                throws IOException

Enabled:

Overrides:

subPrintOn in class NounPattern

IOException

testMatch

void testMatch(EvalContext ctx,
               Object specimen,
               OneArgFunc optEjector)

Description copied from class: Pattern

If this pattern matches the specimen, add macthing bindings to the scope.

Otherwise report the reason why not according to optEjector.

Specified by:

testMatch in class Pattern