[apps/graph/values] Create a class Interval

Change-Id: Ie05a9887c0f3d4146b9e90a139f57e6eec7981b1

apps/graph/Makefile

@@ -12,6 +12,7 @@ app_objs += $(addprefix apps/graph/,\
   list/list_controller.o\
   list/parameter_controller.o\
   values/float_to_string.o\
+  values/interval.o\
   values/title_cell.o\
   values/value_cell.o\
   values/values_controller.o\

apps/graph/values/interval.cpp

@@ -0,0 +1,22 @@
+#include "interval.h"
+#include <assert.h>
+
+Graph::Interval::Interval(float start, float end, float step) :
+	m_start(start),
+	m_end(end),
+	m_step(step)
+{
+}
+
+int Graph::Interval::numberOfElements() {
+	if (m_start > m_end) {
+		return 0;
+	} else {
+		return 1 + (m_end - m_start)/m_step;
+	}
+}
+
+float Graph::Interval::element(int i) {
+	assert(i >= 0 && i < numberOfElements());
+	return m_start + i*m_step;
+}

apps/graph/values/interval.h

@@ -0,0 +1,20 @@
+#ifndef GRAPH_VALUES_INTERVAL_H
+#define GRAPH_VALUES_INTERVAL_H
+
+namespace Graph {
+
+class Interval {
+public:
+  Interval(float start, float end, float step);
+
+  int numberOfElements();
+  float element(int i);
+private:
+  float m_start;
+  float m_end;
+  float m_step;
+};
+
+}
+
+#endif