org.erights.e.elang.evm
Class FinalPattern

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.FinalPattern

All Implemented Interfaces:

Cloneable, EPrintable, MatchMaker

public class FinalPattern

extends NounPattern

Safe: BNF: ID ':' expr

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

      def value := valueGuard coerce(specimen, XXX)

 

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

But wait! That scope includes the value 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 FinalPattern) imposes a well-formedness criterea that allows us to evaluate in the wrong order without effect. A circular user-level final-pattern must be translated into a well-formed kernel-level FinalPattern.

Author:

Mark S. Miller

See Also:

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

Field Summary

private EExpr

myValueGuard

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

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

FinalPattern(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.
EExpr	getValueGuard() Enabled:
(package private) EExpr	guardExpr()
(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, subPrintOn

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

myValueGuard

private final EExpr myValueGuard

Constructor Detail

FinalPattern

public FinalPattern(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 FinalPattern would not be well-formed, throw a (XXX to be defined) exception instead.

FinalPattern

public FinalPattern(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

getValueGuard

public EExpr getValueGuard()

Enabled:

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