org.quasiliteral.quasiterm
Class QHole

java.lang.Object
  |
  +--org.quasiliteral.quasiterm.QAstroArg
        |
        +--org.quasiliteral.quasiterm.QAstro
              |
              +--org.quasiliteral.quasiterm.QHole

All Implemented Interfaces:

Astro, AstroArg, Marker, MatchMaker, PassByConstruction, Persistent, Selfless, Serializable, ValueMaker

Direct Known Subclasses:

QAtHole, QDollarHole

public abstract class QHole

extends QAstro

Untamed: Represents a dollar-hole ("${}") or an at-hole ("@{}") that may be a functor-hole or a term-hole, and that may or may not insist on a tag.

Author:

Mark S. Miller

See Also:

Serialized Form

Field Summary

(package private) int	myHoleNum
(package private) boolean	myIsFunctorHole
(package private) AstroTag	myOptTag
(package private) static long	serialVersionUID

Fields inherited from class org.quasiliteral.quasiterm.QAstroArg

EListGuard, EMPTY_INDEX, myBuilder, myOptSpan

Fields inherited from interface org.erights.e.elib.tables.Selfless

HONORARY, HONORED_NAMES

Fields inherited from interface org.erights.e.elib.serial.PassByConstruction

HONORARY, HONORED_NAMES

Fields inherited from interface org.erights.e.elib.serial.Persistent

HONORARY, HONORED_NAMES

Constructor Summary

(package private)

QHole(AstroBuilder builder, AstroTag optTag, int holeNum, boolean isFunctorHole, SourceSpan optSpan) Makes a hole that matches a term (either a substitution-arg or a specimen), and either evaluates to it (if this is a dollar-hole) or extracts it (if this is an at-hole).

Method Summary

(package private) abstract QHole	asTagged(Astro ident)
ConstList	getArgs() Enabled: A hole itself has no args, even though a term-hole will match a corresponding literal term that does.
int	getHeight() Enabled: A hole is a leaf, and so has height 1
Object	getOptData() Enabled: Holes have no data, so getOptData/0 always returns null.
AstroTag	getTag() Enabled: Tagged holes return their tag, otherwise throws.
private Astro	leafTag(String tagName)
static Object	multiGet(ConstList args, int holeNum, int[] index, boolean repeat) Enabled: Given a multi-dimensional list and an index path, retrieve the corresponding element of the list.
static Object	multiPut(FlexList bindings, int holeNum, int[] index, Object newValue) Enabled: Given a multi-dimensional list and an index path, put newValue at that position in the list.
(package private) Astro	optCoerce(Object termoid) Does 'termoid' coerced to an Astro match the pattern represented by this hole?
Astro	withArgs(ConstList qArgs) Enabled: Can only do this to a functor-hole, in which case it makes a QTerm.
Astro	withoutArgs() Enabled: A hole itself has no args, so this just returns itself.

Methods inherited from class org.quasiliteral.quasiterm.QAstro

asFunctor, build, getOptArgData, getOptArgData, getOptArgString, getOptString, getOptTagCode, matchBind, matchBind, substitute

Methods inherited from class org.quasiliteral.quasiterm.QAstroArg

__printOn, asText, endShape, getOptSpan, matchBindSlice, prettyPrintOn, qbuild, startShape, substSlice, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.quasiliteral.astro.AstroArg

getOptSpan

Methods inherited from interface org.erights.e.elib.tables.Selfless

getSpreadUncall

Field Detail

serialVersionUID

static final long serialVersionUID

myOptTag

final AstroTag myOptTag

myHoleNum

final int myHoleNum

myIsFunctorHole

final boolean myIsFunctorHole

Constructor Detail

QHole

QHole(AstroBuilder builder,
      AstroTag optTag,
      int holeNum,
      boolean isFunctorHole,
      SourceSpan optSpan)

Makes a hole that matches a term (either a substitution-arg or a specimen), and either evaluates to it (if this is a dollar-hole) or extracts it (if this is an at-hole).

Parameters:

builder - Used to build the result of a substitute.

optTag - If present, represents the token tag that the corresponding literal term must have, and this is a tagged-hole. If this is a dollar-hole, the corresponding literal term must be the substitution are at myHoleNum. If this is an at-hole, the corresponding literal term is the specimen.

holeNum - Which hole am I? If this is a dollar-hole, then this says which substitution-arg. If this is an at-hole, then this says which binding.

isFunctorHole - If true, then the corresponding literal term must be 0-arity. If false, then the corresponding literal term may itself have any argument list, and this is a termHole.

optSpan - Where was the source text this node was extracted from?

Method Detail

multiGet

public static Object multiGet(ConstList args,
                              int holeNum,
                              int[] index,
                              boolean repeat)

Enabled: Given a multi-dimensional list and an index path, retrieve the corresponding element of the list.

For example, if 'args' is [['a','b'],['c','d','e']], 'holeNum' is 1, 'index' is [2,3], and 'repeat' is true, then the answer should be 'e', since it's at args[1][2], and the repeat flag allows us to ignore the 3 when we find that 'e' isn't a list. If 'repeat' had been false, the presence of an additional step on the index path would have caused an exception to be thrown. In either case, if an index step is out of bounds, an exception is thrown regardless of the value of 'repeat'.

multiPut

public static Object multiPut(FlexList bindings,
                              int holeNum,
                              int[] index,
                              Object newValue)

Enabled: Given a multi-dimensional list and an index path, put newValue at that position in the list.

For example, if 'bindings' is [['a','b'],['c','d','e']] diverge(), 'holeNum' is 1, 'index' is [2], and 'newValue' is 'x', then the 'e' should be replaced with 'x', since it's at list[1][2]. If any index step is out of bounds, the corresponding list is grown to include it (see FlexList.ensureSize(int) and null is returned. Alternatively, if an old value is being overwritten, then that old value is also returned.

optCoerce

Astro optCoerce(Object termoid)

Does 'termoid' coerced to an Astro match the pattern represented by this hole?

When this hole is a dollar-hole, termoid will be a substitution-arg. When this hole is an at-hole, termoid will be the specimen. In either case, the same criteria are applied:

• If termoid doesn't coerce to an Astro, then null -- we have no match
• If we have a tag, and it doesn't match termoid's tag, then null.
• If we are a functor-hole (rather than a term-hole) and termoid has one or more arguments, then null.
• Otherwise, we match, so return the coerced termoid.

The coercion rules are:

• An integer coerces to a literal integer term.
• A floating point number coerces to a literal float64 term.
• A character coerces to a literal character term.
• null coerces to term`null`, ie, a term with tag "null" and no arguments.
• A boolean coerces to either term`true` or term`false`.
• A String or Twine normally coerces to a zero-arity term whose tag is that String. But if this hole's tag is ".String.", then the String will instead convert to a literal string term.

leafTag

private Astro leafTag(String tagName)

getTag

public AstroTag getTag()

Enabled: Tagged holes return their tag, otherwise throws.

getOptData

public Object getOptData()

Enabled: Holes have no data, so getOptData/0 always returns null.

getArgs

public ConstList getArgs()

Enabled: A hole itself has no args, even though a term-hole will match a corresponding literal term that does.

Returns:

An empty list of QAstroAr

withoutArgs

public Astro withoutArgs()

Enabled: A hole itself has no args, so this just returns itself.

withArgs

public Astro withArgs(ConstList qArgs)

Enabled: Can only do this to a functor-hole, in which case it makes a QTerm.

getHeight

public int getHeight()

Enabled: A hole is a leaf, and so has height 1

Specified by:

getHeight in class QAstroArg

asTagged

abstract QHole asTagged(Astro ident)