if (changed2.isChanged) {
formula1 = new For(for1.getVariable(), for1.getType(), formula2);
changed1.isChanged = true;
}
} else if (formula instanceof Ex){
Ex ex = (Ex)formula;
Changed changed2 = new Changed();
Formula formula2 = compress(ex.getFormula(), changed2);
if (changed2.isChanged){
formula1 = new Ex(ex.getVariable(), ex.getType(), formula2);
changed1.isChanged = true;
}
}
if (changed1.isChanged){
formula1 = compress(formula1, new Changed());