// Single line.
Argument arg = ArgumentParser.parseArgument(string, knownArguments, clipboard, mathCollection);
if (arg!=null) {
Selection selection = mathCollection.getSelection();
Equation appendedEquation = new Equation(arg);
selection.appendEquation(appendedEquation);
}
} else {
// Multiple lines.
for (String next : lines) {
Equation e = mathCollection.processLine(next);