[apps/graph/values] Create a class Interval

Change-Id: Ie05a9887c0f3d4146b9e90a139f57e6eec7981b1

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;
+}