Looking into Image locking problems [1] caused by a recursive array such as
this...
literalArray := #( 1 2 3 ).
literalArray at: 3 put: literalArray.
I find that "literalArray printString" locks the image due to
Array>>printOn: use of the recursive #shouldBePrintedAsLiteral method. Now
its implementation is identical to #isLiteral and indeed "literalArray
isLiteral" also locks the Image. So comparing implementors of #isLiteral...
Object>>isLiteral ^false
Boolean>>isLiteral ^true
Character>>isLiteral ^true
Integer>>isLiteral ^true
String>>isLiteral ^true
UndefinedObject>>isLiteral ^true
ByteArray>>isLiteral ^self class == ByteArray
Float>>isLiteral ^self isFinite "^(self - self) = 0.0"
ScaledDecimal>>isLiteral ^denominator = 1 or: [(10 raisedTo:
scale)\\denominator = 0]
Array>>isLiteral ^self class == Array and: [self allSatisfy: [:each |
each isLiteral]]
...I find most are very basic (might even say deterministic), with the
recursion of Array>>isLiteral seeming an annomaly. Also, the big IF
condition in Array>>printOn: smells like a design decision being made at
runtime (Valloud AMCOS p12).
Array>>printOn: aStream
self shouldBePrintedAsLiteral ifTrue: [self printAsLiteralFormOn: aStream.
^ self].
self isSelfEvaluating ifTrue: [self printAsSelfEvaluatingFormOn: aStream. ^
self].
super printOn: aStream
Flipping between two printString formats seems like selecting between two
class types. Indeed, if we had a LiteralArray class, there would be no need
for its printOn: to recursively search to determine its form, thus allowing
#printStringLimitedTo: to do its thing to protect against infinite
recursion.
Also, instead of a recursive Array>>isLiteral we'd have something like
LiteralArray>>isLiteral ^true
Array>>isLiteral ^false
which seems to align much better with the pattern of the other #isLiteral
implementors.
I notice there is both RBArrayNode and RBLiteralArrayNode.
So what are the wider concerns that might apply?
(In particular, I'm not sure how the #isSelfEvaluating (which is also
recursive) fits into the big picture)
cheers -ben
[1] https://www.mail-archive.com/[email protected]/msg25156.html
