SPARQL Christmas tree

christmas_tree.rq

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

SELECT ?line
WHERE {
  VALUES ?row { 1 2 3 4 5 6 7 }
  
  # Width of the widest row (9 stars + 2 spaces = 11 total)
  BIND(11 AS ?width)
  
  # Calculate number of stars for this row
  BIND(IF(?row <= 5, (2 * ?row) - 1, 1) AS ?numStars)
  
  # Calculate spaces on each side
  BIND((?width - ?numStars) / 2 AS ?numSpaces)
  
  # Generate the line with balanced spacing
  BIND(SUBSTR("          ", 1, ?numSpaces) AS ?spacePart)
  BIND(SUBSTR("*********", 1, ?numStars) AS ?starPart)
  
  BIND(CONCAT(?spacePart, ?starPart, ?spacePart) AS ?line)
}
ORDER BY ?row