Problem Statement

Remove a specific line or a number of lines from a file. This should be implemented as a routine that takes three parameters (filename, starting line, and the number of lines to be removed). For the purpose of this task, line numbers and the number of lines start at one, so to remove the first two lines from the file foobar.txt, the parameters should be: foobar.txt, 1, 2 Empty lines are considered and should still be counted, and if the specified line is empty, it should still be removed. An appropriate message should appear if an attempt is made to remove lines beyond the end of the file.

Let's start with the solution:

IMPORT STD;
RemoveLines(logicalfile, startline, numlines) := FUNCTIONMACRO
  EndLine := startline + numlines - 1;
  RecCnt  := COUNT(logicalfile);
  Res := logicalfile[1..startline-1] + logicalfile[endline+1..];
  RETURN WHEN(IF(RecCnt < EndLine,logicalfile,Res), 
              IF(RecCnt < EndLine,STD.System.Log.addWorkunitWarning('Attempted removal past end of file-removal ignored')));
ENDMACRO;


MyFile := DATASET(100,TRANSFORM({UNSIGNED1 RecID},SELF.RecID := COUNTER));
RemoveLines(MyFile,3,10);