From 4ccadc4f3692b4f31859deb547fb5adeaf4be92b Mon Sep 17 00:00:00 2001
From: Dion Moult <dion@thinkmoult.com>
Date: Fri, 6 Aug 2021 12:38:34 +1000
Subject: [PATCH] New unit utility to auto detect SI unit dimensional exponents

---
 .../ifcopenshell/util/unit.py                 | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/src/ifcopenshell-python/ifcopenshell/util/unit.py b/src/ifcopenshell-python/ifcopenshell/util/unit.py
index c29dafb44a..d9ee421c56 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/unit.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/unit.py
@@ -52,6 +52,40 @@ unit_names = [
     "WEBER",
 ]
 
+si_dimensions = {
+    "METRE": (1, 0, 0, 0, 0, 0, 0),
+    "SQUARE_METRE": (2, 0, 0, 0, 0, 0, 0),
+    "CUBIC_METRE": (3, 0, 0, 0, 0, 0, 0),
+    "GRAM": (0, 1, 0, 0, 0, 0, 0),
+    "SECOND": (0, 0, 1, 0, 0, 0, 0),
+    "AMPERE": (0, 0, 0, 1, 0, 0, 0),
+    "KELVIN": (0, 0, 0, 0, 1, 0, 0),
+    "MOLE": (0, 0, 0, 0, 0, 1, 0),
+    "CANDELA": (0, 0, 0, 0, 0, 0, 1),
+    "RADIAN": (0, 0, 0, 0, 0, 0, 0),
+    "STERADIAN": (0, 0, 0, 0, 0, 0, 0),
+    "HERTZ": (0, 0, -1, 0, 0, 0, 0),
+    "NEWTON": (1, 1, -2, 0, 0, 0, 0),
+    "PASCAL": (-1, 1, -2, 0, 0, 0, 0),
+    "JOULE": (2, 1, -2, 0, 0, 0, 0),
+    "WATT": (2, 1, -3, 0, 0, 0, 0),
+    "COULOMB": (0, 0, 1, 1, 0, 0, 0),
+    "VOLT": (2, 1, -3, -1, 0, 0, 0),
+    "FARAD": (-2, -1, 4, 2, 0, 0, 0),
+    "OHM": (2, 1, -3, -2, 0, 0, 0),
+    "SIEMENS": (-2, -1, 3, 2, 0, 0, 0),
+    "WEBER": (2, 1, -2, -1, 0, 0, 0),
+    "TESLA": (0, 1, -2, -1, 0, 0, 0),
+    "HENRY": (2, 1, -2, -2, 0, 0, 0),
+    "DEGREE_CELSIUS": (0, 0, 0, 0, 1, 0, 0),
+    "LUMEN": (0, 0, 0, 0, 0, 0, 1),
+    "LUX": (-2, 0, 0, 0, 0, 0, 1),
+    "BECQUEREL": (0, 0, -1, 0, 0, 0, 0),
+    "GRAY": (2, 0, -2, 0, 0, 0, 0),
+    "SIEVERT": (2, 0, -2, 0, 0, 0, 0),
+    "OTHERWISE": (0, 0, 0, 0, 0, 0, 0)
+}
+
 si_conversions = {
     "inch": 0.0254,
     "foot": 0.3048,
@@ -110,6 +144,10 @@ def get_unit_name(text):
             return name
 
 
+def get_si_dimensions(name):
+    return si_dimensions.get(name, si_dimensions["OTHERWISE"])
+
+
 def convert(value, from_prefix, from_unit, to_prefix, to_unit):
     """Converts between length, area, and volume units