From 604e2211abc1b46470d382a1f9365d81e50f1126 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89milie=20Feral?= <emilie.feral@numworks.com>
Date: Mon, 10 Oct 2016 17:28:08 +0200
Subject: [PATCH] [apps/graph/function] Add a method to evaluate the function

Change-Id: I54516369bbbde8d65d98ad41d6e94cd3780e6162
---
 apps/graph/function.cpp | 7 +++++++
 apps/graph/function.h   | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/apps/graph/function.cpp b/apps/graph/function.cpp
index d0e6a316f..f96a0c8e7 100644
--- a/apps/graph/function.cpp
+++ b/apps/graph/function.cpp
@@ -58,3 +58,10 @@ bool Graph::Function::isActive() {
 void Graph::Function::setActive(bool active) {
   m_active = active;
 }
+
+float Graph::Function::evaluateAtAbscissa(float x) {
+  Context plotContext;
+  Float xExp = Float(x);
+  plotContext.setExpressionForSymbolName(&xExp, "x");
+  return m_expression->approximate(plotContext);
+}
diff --git a/apps/graph/function.h b/apps/graph/function.h
index 58d2b3fb1..154fefeba 100644
--- a/apps/graph/function.h
+++ b/apps/graph/function.h
@@ -9,6 +9,7 @@ namespace Graph {
 class Function {
 public:
   static constexpr const char * Parameter = "(x)";
+
   Function(const char * text = nullptr, KDColor color = KDColorBlack);
   ~Function(); // Delete expression and layout, if needed
   const char * text();
@@ -20,6 +21,7 @@ public:
   void setActive(bool active);
   void setContent(const char * c);
   void setColor(KDColor m_color);
+  float evaluateAtAbscissa(float x);
 private:
   constexpr static int k_bodyLength = 255;
   char m_text[k_bodyLength];