Adds utility to stringize station values

src/ifcopenshell-python/ifcopenshell/util/stationing.py

@@ -0,0 +1,51 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2021 Thomas Krijnen <thomas@aecgeeks.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import math
+
+def station_as_string(station:float,plus_seperator=3,accuracy=3):
+    """
+    Returns a stringized version of a station. Example 100.0 is 1+00.00 as a stationing string
+    @param station: the station to be stringized
+    @param plus_seperator: location of the '+' symbol relative to the decimal place (typically 2 for US units and 3 for SI units)
+    @param accuracy: number of digits following the decimal place
+    """
+    value = math.fabs(station)
+
+    shifter = math.pow(10.0,plus_seperator)
+    v1 = math.floor(value/shifter)
+    v2 = value - v1*shifter
+
+    # Check to make sure that v2 is not basically the same as shifter
+    # If station = 69500.00000, we sometimes get 694+100.00 instead of 695+00.00
+    if math.isclose(v2-shifter,5.0*math.pow(10.0,-(accuracy+1))):
+        v2 = 0.0
+        v1 += 1
+
+    v1 = -1*v1 if station < 0 else v1
+
+    station_string = "{:d}+{:0{}.{}f}".format(v1,v2,plus_seperator+accuracy+1,accuracy)
+
+    # special case when v1 is 0 and station is negative, the string above doesn't get the leading 
+    # negative sign. this snippet fixes that
+    if v1 == 0 and station < 0:
+        station_string = "-" + station_string
+
+    return station_string
+
+

src/ifcopenshell-python/test/util/test_stationing.py

@@ -0,0 +1,45 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2021 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import ifcopenshell.util.stationing as sta
+
+def test_station_as_string():
+    # test with a bunch of "random" station values
+    s = sta.station_as_string(0.0)
+    assert(s == "0+000.000")
+
+    s = sta.station_as_string(0.0,2,2)
+    assert(s == "0+00.00")
+
+    s = sta.station_as_string(0.0,2)
+    assert(s == "0+00.000")
+
+    s = sta.station_as_string(100.00)    
+    assert(s == "0+100.000")
+
+    s = sta.station_as_string(-100.00)    
+    assert(s == "-0+100.000")
+
+    s = sta.station_as_string(123456.789,2,2)    
+    assert(s == "1234+56.79")
+
+    s = sta.station_as_string(-123456.789,2,2)    
+    assert(s == "-1234+56.79")
+
+    s = sta.station_as_string(123456.789,3,4)    
+    assert(s == "123+456.7890")