vlookup

Question

Hi everyone, 
 
 I'm having a table, 1st column is the input variable and all the other columns are different outputs. I was looking of a way to do some sorte of a vlookup (like in excel) and get the correct output according to the input i choose. Any ideas? 
 
 Thanks

Mueller · Answer

Hi Pedro, The most likely solution is to use a keyed table. Information about record and table types are in the GC help under GCScript Programming > Components of the GCScript Language > Fundamental Types > Record and Table Types (here the relevant excerpt, especially the lookup/conversion table example at the bottom): The Table Type 
 A table is an associative collection of keys and values. In some other programming languages, this kind of collection is called a dictionary. 
 One way to define a table is &ldquo;in line&rdquo;. The general form is: 
 
 {[keyExpression]=valueExpression, [keyExpression]=valueExpression, &hellip; } 
 
 Note that each keyExpression is enclosed in square brackets. That's what distinguishes table-creation notation from record-creation notation. 
 Each keyExpression and valueExpression may resolve to a value of any type. (Only those resultant values are stored in the table.) 
 Here&rsquo;s an example: 
 
 table tab = {[5]='five', [line01]=line01.Length, ['how now']='brown cow', [Sqrt(16)]=Series(1,10,1)} 
 
 Alternatively, we can construct a table programmatically: 
 
 table tab = {};
	tab.Add(5, 'five');
	tab.Add(line01, line01.Length);
	tab.Add('how now', 'brown cow');
	double key = Sqrt(16);
	int[] value = Series(1,10,1);
	tab.Add(key, value); 
 
 Regardless of how it&rsquo;s been created, you can use a table instance in the same way we would use a list, except that the index key can be any object rather than (necessarily) an integer: 
 
 Print(tab['how now']); // Prints "brown cow".
	Print(tab[4]}; // Prints "{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}".
	tab[line01] = point02.X; 
 
 One purpose of a table is to preserve a set of values so that they can be compared later. For example: 
 
 // Create and populate the table.
	
	global table lineLengths = {}; // Create an empty table.
	var lines = Nodes(n => n is Line); // Get all of the Line nodes in the GC model.
	foreach (line in lines) // Add the length of each line to the table,
 lineLengths.Add(line, line.Length); // keyed by the line, itself.
	
	// Do something that causes one or more lines to change.
	
	// Then, afterwards...
	
	foreach (line in table.Keys()) // Step through all of the keys in the table, which are 
	{ // (still) all of the Line nodes we're interested in.
 var diff = line.Length &ndash; lineLengths[line]; // If the line's length has changed, show
 if (diff != 0) // the difference in the script console..
 PrintFormat("The length of {0} has changed by {1}.", line, diff);
	} 
 
 Another purpose of a table is to serve as a lookup/conversion table. For example: 
 
 global table casementSizes = { // Each key is a casement model number. Each value is a record
 // providing the height and width dimensions of that model.
	
 [1824]={height=2.0, width=1.5},
 [1828]={height=2.4, width=1.5},
 [1836]={height=3.0, width=1.5},
	
 ... (etc.) ...
 };;
	
	// Subsequently, we might enter the following expression into the YTranslation property of
	// one of our Point nodes. (Imagine we also have an Expression node named "casementNumber".)
	
	casementSizes[casementNumber].Height

HTH, Volker

Mueller · Answer

Hi Pedro, 
 Looking at your script Descarregador2.gct I don't see where you declare the table WES. At the same time I see that you use the table WES if it were a Structure (e.g. WES[m].r1Hd). IF you intend WES[m] to have the value r1HD, then you need somewhere (probably in a Script Transaction) to declare the table (table WES = { };) and later a statement like WES.Add(m, r1HD). Then, accessing WES[m] will yield the value of r1HD, so you'd just need to use WES[m] to retrieve r1HD. This means a statement like double r1 = WES[m] * H; should be valid. This works, if m is the same value when adding the table entry and when retrieving it. If there is the slightest deviation between the value of m used when adding an entry to WES[m], i.e. WES.Add(m, r1HD); and the value of m when retrieving the entry of WES[m], then you may get an error for attempting to access a table entry that does not exist. 
 In the attached GCT, transaction 7 declares table WES, transaction 8 defines a function to Add an entry to a table and uses it in functionCall1 to add an entry to WES based on the inputs from m and H0, and transaction 9 adds expression01, retrieving the value of H0 based on the key m from table WES. 
 HTH, 
 Volker 
 https://communities.bentley.com/cfs-file/__key/communityserver-discussions-components-files/360/Descarregador2a.gct