[apps] Sequence: enable to defined dependent sequences

apps/sequence/sequence_context.cpp

@@ -0,0 +1,66 @@
+#include "sequence_context.h"
+#include "sequence_store.h"
+#include <cmath>
+
+using namespace Poincare;
+
+namespace Sequence {
+
+template<typename T>
+TemplatedSequenceContext<T>::TemplatedSequenceContext() :
+  m_rank(-1),
+  m_values{{NAN, NAN, NAN},{NAN, NAN, NAN}}
+{
+}
+
+template<typename T>
+T TemplatedSequenceContext<T>::valueOfSequenceAtPreviousRank(int sequenceIndex, int rank) const {
+  return m_values[sequenceIndex][rank];
+}
+
+template<typename T>
+void TemplatedSequenceContext<T>::resetCache() {
+  m_rank = -1;
+}
+
+template<typename T>
+bool TemplatedSequenceContext<T>::iterateUntilRank(int n, SequenceStore * sequenceStore, SequenceContext * sqctx) {
+  if (m_rank > n) {
+    m_rank = -1;
+  }
+  if (n < 0 || n-m_rank > k_maxRecurrentRank) {
+    return false;
+  }
+  while (m_rank++ < n) {
+    step(sequenceStore, sqctx);
+  }
+  m_rank--;
+  return true;
+}
+
+template<typename T>
+void TemplatedSequenceContext<T>::step(SequenceStore * sequenceStore, SequenceContext * sqctx) {
+  /* Shift values */
+  for (int i = 0; i < MaxNumberOfSequences; i++) {
+    for (int j = MaxRecurrenceDepth; j > 0; j--) {
+      m_values[i][j] = m_values[i][j-1];
+    }
+    m_values[i][0] = NAN;
+  }
+
+  /* Evaluate new u(n) and v(n) */
+  Sequence * u = sequenceStore->numberOfFunctions() > 0 ? sequenceStore->functionAtIndex(0) : nullptr;
+  u = u && u->isDefined() ? u : nullptr;
+  Sequence * v = sequenceStore->numberOfFunctions() > 1 ? sequenceStore->functionAtIndex(1) : nullptr;
+  v = v && v->isDefined() ? v : nullptr;
+
+  /* TODO: explain */
+  m_values[0][0] = u ? u->approximateToNextRank<T>(m_rank, sqctx) : NAN;
+  m_values[1][0] = v ? v->approximateToNextRank<T>(m_rank, sqctx) : NAN;
+  m_values[0][0] = u ? u->approximateToNextRank<T>(m_rank, sqctx) : NAN;
+}
+
+template class TemplatedSequenceContext<float>;
+template class TemplatedSequenceContext<double>;
+
+}