add sinc function

src/nmreval/models/basic.py

@@ -191,6 +191,18 @@ class PowerLawCross:
         return ret_val
 
 
+class Sinc:
+    type = 'Basic'
+    name = 'Sinc'
+    equation = 'C * sinc((x-x_{0})/w)'
+    params = ['C', 'x_{0}', 'w']
+
+    @staticmethod
+    def func(x, c: float, x0: float, w: float):
+        # numpy sinc is defined as sin(pi*x)/(pi*x)
+        return c * np.sinc(((x-x0)/w)/np.pi)
+
+
 class Sine:
     """
     Wavy sine function