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[poincare] Power::shallowReduce: (a^b)^c should not be applied in Real

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mode with (x^(1/2))^2.
This commit is contained in:
Émilie Feral
2019-09-20 10:02:45 +02:00
committed by LeaNumworks
parent 22c7fb440e
commit 7525ee3ffc
1 changed files with 20 additions and 13 deletions
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33
poincare/src/power.cpp
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@@ -629,23 +629,30 @@ Expression Power::shallowReduce(ExpressionNode::ReductionContext reductionContex
*/
if (baseType == ExpressionNode::Type::Power) {
Power powerBase = static_cast<Power &>(base);
// Check if a > 0 or c is Integer
if (powerBase.childAtIndex(0).sign(reductionContext.context()) == ExpressionNode::Sign::Positive // a > 0
|| (indexType == ExpressionNode::Type::Rational && static_cast<Rational &>(index).isInteger())) // c integr
{
/* If the complexFormat is real, we check that the inner power is defined
* before applying the rule (a^b)^c -> a^(b*c). Otherwise, we return
* 'unreal'. */
if (reductionContext.complexFormat() == Preferences::ComplexFormat::Real) {
Expression approximation = powerBase.approximate<float>(reductionContext.context(), reductionContext.complexFormat(), reductionContext.angleUnit());
if (approximation.type() == ExpressionNode::Type::Unreal) {
replaceWithInPlace(approximation);
return approximation;
}
bool applyRule = powerBase.childAtIndex(0).sign(reductionContext.context()) == ExpressionNode::Sign::Positive // a > 0
|| (indexType == ExpressionNode::Type::Rational && static_cast<Rational &>(index).isInteger()); // c integer
/* If the complexFormat is real, we check that the inner power is defined
* before applying the rule (a^b)^c -> a^(b*c). Otherwise, we return
* 'unreal' or we do nothing. */
if (reductionContext.complexFormat() == Preferences::ComplexFormat::Real) {
Expression approximation = powerBase.approximate<float>(reductionContext.context(), reductionContext.complexFormat(), reductionContext.angleUnit());
if (approximation.type() == ExpressionNode::Type::Unreal) {
// The inner power is unreal, return "unreal"
replaceWithInPlace(approximation);
return approximation;
} else if (approximation.type() == ExpressionNode::Type::Undefined) {
/* The inner power is undefined, it can be 'x^(1/2)' for instance. We
* don't want to simplify this as it could be unreal with x = -2 but
* also real with x = 2. */
applyRule = false;
}
}
if (applyRule) {
return simplifyPowerPower(reductionContext);
}
}
// Step 11: (a*b*c*...)^r ?
if (!letPowerAtRoot && baseType == ExpressionNode::Type::Multiplication) {
Multiplication multiplicationBase = static_cast<Multiplication &>(base);