Creating a list in an Expression

Question

Hi All, 
 Another function question. 
 We are looking to find the corner angles of an array of facade panels. 
 Looking through the function list it appears easy enough to find the corner angle of a (planar) polygon using the Angle() function. 
 But this is just for a single polygon. 
 we would like to place some blinds on each panel related to the corner angle of each polygon, which does change on every panel. 
 So as a solution I created an output to excel and then ran a script transaction to achieve the result we were looking for in generating an angle for each panel. 
 for those interested i this is the script transaction 
 t ransaction 12 script 'Export to excel' { string cellname = "A"; double cellnumber = 1; for (int i = 0; i < watch1.Count; ++i) { excelRange1.Value = Angle(watch1[i].Vertices[3],watch1[i].Vertices[2],watch1[i].Vertices[0]); cellnumber = 1 + i; cellname = "A" + cellnumber; excelRange1.RangeAddress = cellname; UpdateGraph(); } } 
 To make it simple for this test i flattened the polygon1 array using a watch and then as you can see above referenced this as the index for each polygon. 
 This works well and gives a list of angles for the given corner of each polygon. 
 We can then take this back in from excel to use as a rotation for our bind box. 
 My question is: 
 Is there a way to achieve this without the use of excel? 
 I tried to develop an expression to gather the angles into a list but I kept running into errors. (mostly my own knowledge) 
 Any suggestions would be appreciated. 
 Attached is a sample DGN/script 
 Thanks 
 Wayne 
 
 Measure_Panel_Angles.dgn

Mueller · Accepted Answer

Hi Wayne, 
 Alternatively, you could write similar code in a function and let the function return a list or an array of values: 
 double[][] function (Polygon[][] polyArray)
{
 double[][] retValue = {};

 for (int i = 0; i < polyArray.Count; ++i)
 {
 retValue[i] = {};
 
 for (int j = 0; j < polyArray[i].Count; ++j)
 {
 retValue[i][j] = Angle(polyArray[i][j].Vertices[3], polyArray[i][j].Vertices[2], polyArray[i][j].Vertices[0]);
 }
 }
 return retValue;
}
 
 This would be the "Function" input property for a FunctionCall node. After wiring your polygon array to the input property "polyArray", this FunctionCall node will return an array of double values which are the angles between the vertices indicated in your script. 
 HTH, 
 Volker

Mueller · Answer

Hi Wayne, 
 It'll work without the double[][] preceding the function keyword. It's just a habit of mine to use strong typing whenever possible, also for function signatures. In some situations the compiler might catch type mismatches and help keep the script healthy and happy. In some situations that happens in GC, too; apparently,in this case it does not matter. 
 Yes, for an array of strings (or a list of lists of strings) you would use string[][]. The pairs of square brackets indicate the depth of nesting. One pair means a simple list, two pairs a list of lists, three pairs (string[][][]) list of lists of lists, etc. 
 If you are unsure what nesting will result from actions, then no typing might be the best course of action; however, on the receiving end one would need to take corresponding precautions to avoid referencing too deeply into data. 
 Best regards, 
 Volker

Creating a list in an Expression

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