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[Sequences] Fixed a few crashes

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Change-Id: Ib929bbae0f9ca06409706336ff799075e1288694
This commit is contained in:
Arthur Camouseigt
2020-09-17 11:43:27 +02:00
committed by Émilie Feral
parent 26bbdead7d
commit 960335c330
7 changed files with 60 additions and 16 deletions
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39
apps/shared/sequence.cpp
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@@ -7,6 +7,8 @@
#include <poincare/sum.h>
#include <poincare/vertical_offset_layout.h>
#include <poincare/integer.h>
#include <poincare/rational.h>
#include <poincare/addition.h>
#include "../shared/poincare_helpers.h"
#include <string.h>
#include <apps/i18n.h>
@@ -131,6 +133,40 @@ bool Sequence::isEmpty() {
(type == Type::SingleRecurrence || data->initialConditionSize(1) == 0)));
}
bool Sequence::badlyReferencesItself(Context * context) {
Expression e = expressionReduced(context);
bool value = e.hasExpression([](Expression e, const void * sequencePointer) {
if (e.type() != ExpressionNode::Type::Sequence) {
return false;
}
Sequence * seq = (Sequence *)(sequencePointer);
const char * symbolName = static_cast<Symbol&>(e).name();
/* symbolName is either u, v or w while seq->fullName has the extention .seq
* at the end. Therefore we cannot use strcmp on the two strings. We just
* want to check if the first char are identical*/
if (strncmp(symbolName, seq->fullName(), strlen(symbolName)) == 0) {
/* The expression of the sequence contains a reference to itself.
* We must check if the sequence can be calculated before continuing
* If the sequence is of explicit type, it cannot reference itself.
* If the sequence is of SingleRecurrent type, it can be defined by:
* u(initialRank and u(n).
* If the sequence is of DoubleRecurrent type, it can be defined by:
* u(initialRank), u(initialRank+1), u(n) and u(n+1).
* In any other case, the value of the sequence cannot be computed.
* We therefore return NAN. */
Expression rank = e.childAtIndex(0);
if (seq->type() == Sequence::Type::Explicit ||
(!(rank.isIdenticalTo(Rational::Builder(seq->initialRank())) || rank.isIdenticalTo(Symbol::Builder(UCodePointUnknown))) &&
(seq->type() == Sequence::Type::SingleRecurrence || (seq->type() == Sequence::Type::DoubleRecurrence && !(rank.isIdenticalTo(Rational::Builder(seq->initialRank()+1)) || rank.isIdenticalTo(Addition::Builder(Symbol::Builder(UCodePointUnknown), Rational::Builder(1))))))))
{
return true;
}
}
return false;
}, reinterpret_cast<const void *>(this));
return value;
}
template<typename T>
T Sequence::templatedApproximateAtAbscissa(T x, SequenceContext * sqctx) const {
T n = std::round(x);
@@ -143,7 +179,7 @@ T Sequence::templatedApproximateAtAbscissa(T x, SequenceContext * sqctx) const {
template<typename T>
T Sequence::valueAtRank(int n, SequenceContext *sqctx) {
if (n < 0) {
if (n < 0 || badlyReferencesItself(sqctx)) {
return NAN;
}
int sequenceIndex = SequenceStore::sequenceIndexForName(fullName()[0]);
@@ -174,7 +210,6 @@ T Sequence::approximateToNextRank(int n, SequenceContext * sqctx, int sequenceIn
Poincare::SerializationHelper::CodePoint(unknownN, bufferSize, UCodePointUnknown);
CacheContext<T> ctx = CacheContext<T>(sqctx);
ctx.setSequenceContext(sqctx);
// Hold values u(n), u(n-1), u(n-2), v(n), v(n-1), v(n-2)...
T values[MaxNumberOfSequences][MaxRecurrenceDepth+1];