[apps/probability] Create a class evaluate context for probability app

Change-Id: I38448ddeec25225edad1d96bf89d32d1eb86915d

apps/probability/evaluate_context.cpp

@@ -0,0 +1,39 @@
+#include "evaluate_context.h"
+#include <string.h>
+
+namespace Probability {
+
+EvaluateContext::EvaluateContext(::Context * parentContext) :
+  m_tValue(Float(0.0f)),
+  m_firstParameterValue(Float(0.0f)),
+  m_secondParameterValue(Float(0.0f)),
+  m_context(parentContext)
+{
+}
+
+void EvaluateContext::setOverridenValueForSymbolT(float f) {
+  m_tValue = Float(f);
+}
+
+void EvaluateContext::setOverridenValueForFirstParameter(float f) {
+  m_firstParameterValue = Float(f);
+}
+
+void EvaluateContext::setOverridenValueForSecondParameter(float f) {
+  m_secondParameterValue = Float(f);
+}
+
+const Expression * EvaluateContext::expressionForSymbol(const Symbol * symbol) {
+  if (symbol->name() == 't') {
+    return &m_tValue;
+  }
+  if (symbol->name() == Symbol::SpecialSymbols::p1) {
+    return &m_firstParameterValue;
+  }
+  if (symbol->name() == Symbol::SpecialSymbols::p2) {
+    return &m_secondParameterValue;
+  }
+  return m_context->expressionForSymbol(symbol);
+}
+
+}