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[poincare] Sequence: when approximating within a reduce routine, escape to avoid

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infinite loop
This commit is contained in:
Émilie Feral
2020-11-03 17:40:16 +01:00
parent 7142f9545e
commit 4cc3542a99
1 changed files with 10 additions and 1 deletions
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11
poincare/src/sequence.cpp
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@@ -63,7 +63,16 @@ Evaluation<double> SequenceNode::approximate(DoublePrecision p, ApproximationCon
template<typename T>
Evaluation<T> SequenceNode::templatedApproximate(ApproximationContext approximationContext) const {
if (childAtIndex(0)->approximate((T)1, approximationContext).isUndefined()) {
if (childAtIndex(0)->approximate((T)1, approximationContext).isUndefined() || approximationContext.withinReduce()) {
/* If we're inside a reducing routine, we want to escape the sequence
* approximation. Indeed, in order to know that the sequence is well defined
* (especially for self-referencing or inter-dependently defined sequences),
* we need to reduce the sequence definition (done by calling
* 'expressionForSymbolAbstract'); if we're within a reduce routine, we
* would create an infinite loop. Returning a NAN approximation for
* sequences within reduce routine does not really matter: we just have
* access to less information in order to simplify (abs(u(n)) might not be
* reduced for instance). */
return Complex<T>::Undefined();
}
Expression e = approximationContext.context()->expressionForSymbolAbstract(this, false);