From ee9d616733456b3f8c2135634208669bf2014ccd Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Thu, 26 Feb 2015 23:31:07 -0700
Subject: [PATCH] language/units: add strip_unit function

---
 artiq/language/units.py | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/artiq/language/units.py b/artiq/language/units.py
index c15bf7e01..52a456e3a 100644
--- a/artiq/language/units.py
+++ b/artiq/language/units.py
@@ -239,3 +239,26 @@ def check_unit(value, unit):
     else:
         if not isinstance(value, Quantity) or value.unit != unit:
             raise DimensionError
+
+def strip_unit(value, unit):
+    """Check that the value has the specified unit and returns its amount.
+    Raises ``DimensionError`` if the units does not match.
+
+    If the passed value is not a ``Quantity``, it is assumed to be in the
+    specified unit and is returned unchanged.
+
+    If ``unit`` is ``None``, passing a ``Quantity`` as value raises
+    ``DimensionError``.
+
+    """
+    if unit is None:
+        if isinstance(value, Quantity):
+            raise DimensionError
+        else:
+            return value
+    else:
+        if isinstance(value, Quantity):
+            if value.unit != unit:
+                raise DimensionError
+            else:
+                return value.amount