environment: make NumberValue return integers when appropriate. Closes #397

RELEASE_NOTES.rst

@@ -48,6 +48,9 @@ unreleased [1.0rc3]
     from ARTIQ, trusting that h5py maps and converts types between HDF5 and
     python/numpy "as expected".
 
+* NumberValue now returns an integer if ``ndecimals`` = 0, ``scale`` = 1 and
+  ``step`` is integer.
+
 
 1.0rc2
 ------

artiq/examples/master/repository/arguments_demo.py

@@ -44,6 +44,8 @@ class ArgumentsDemo(EnvExperiment):
         self.setattr_argument("number", NumberValue(42e-6,
                                                     unit="us", scale=1e-6,
                                                     ndecimals=4))
+        self.setattr_argument("integer", NumberValue(42,
+                                                     step=1, ndecimals=0))
         self.setattr_argument("string", StringValue("Hello World"))
         self.setattr_argument("scan", Scannable(global_max=400,
                                                 default=NoScan(325),
@@ -65,7 +67,8 @@ class ArgumentsDemo(EnvExperiment):
         print(self.pyon_value)
         print(self.boolean)
         print(self.enum)
-        print(self.number)
+        print(self.number, type(self.number))
+        print(self.integer, type(self.integer))
         print(self.string)
         for i in self.scan:
             print(i)

artiq/language/environment.py

@@ -78,7 +78,12 @@ class EnumerationValue(_SimpleArgProcessor):
 
 
 class NumberValue(_SimpleArgProcessor):
-    """An argument that can take a numerical value (typically floating point).
+    """An argument that can take a numerical value.
+
+    If ndecimals = 0, scale = 1 and step is integer, then it returns
+    an integer value. Otherwise, it returns a floating point value.
+    The simplest way to represent an integer argument is
+    ``NumberValue(step=1, ndecimals=0)``.
 
     :param unit: A string representing the unit of the value, for user
         interface (UI) purposes.
@@ -94,7 +99,8 @@ class NumberValue(_SimpleArgProcessor):
                  step=None, min=None, max=None, ndecimals=2):
         if step is None:
             step = scale/10.0
-        _SimpleArgProcessor.__init__(self, default)
+        if default is not NoDefault:
+            self.default_value = default
         self.unit = unit
         self.scale = scale
         self.step = step
@@ -102,8 +108,29 @@ class NumberValue(_SimpleArgProcessor):
         self.max = max
         self.ndecimals = ndecimals
 
+    def _is_int(self):
+        return (self.ndecimals == 0
+                and int(self.step) == self.step
+                and self.scale == 1)
+
+    def default(self):
+        if not hasattr(self, "default_value"):
+            raise DefaultMissing
+        if self._is_int():
+            return int(self.default_value)
+        else:
+            return float(self.default_value)
+
+    def process(self, x):
+        if self._is_int():
+            return int(x)
+        else:
+            return float(x)
+
     def describe(self):
-        d = _SimpleArgProcessor.describe(self)
+        d = {"ty": self.__class__.__name__}
+        if hasattr(self, "default_value"):
+            d["default"] = self.default_value
         d["unit"] = self.unit
         d["scale"] = self.scale
         d["step"] = self.step