public Calculator(String[] sa, Map<String, String> vars) {
/* Populates the atom list.
* Also collapses 2-part negative numbers into single Atoms. */
if (vars.size() < 1) throw new IllegalArgumentException("No expression supplied");
this.vars = vars;
Atom atom = null, prePrevAtom;
int prevIndex;
NEXT_TOKEN:
for (String token : sa)
try {
atom = new Atom(token);
prevIndex = atoms.size() - 1;
if (prevIndex < 0) continue;
if (atoms.get(prevIndex).op != MathOp.SUBTRACT) continue;
prePrevAtom = (prevIndex > 0) ? atoms.get(prevIndex - 1) : null;
if (prePrevAtom != null && !TradOrLParen.contains(prePrevAtom.op)) continue;
if (atom.op == null) {
atoms.remove(prevIndex);
atom.val *= -1;
} else if (atom.op == MathOp.LPAREN) {
atoms.remove(prevIndex);
atoms.add(new Atom(-1L));
atoms.add(new Atom(MathOp.MULTIPLY));
}
} finally {
atoms.add(atom);
}
}
/**
* If atoms[startAtomIndex] == '(', then last visited atoms will be the next top-level (un-paired)
* ')'. Otherwise, all remainign atoms will be visited. Every visited atom will be removed from
* 'atoms'.
*
* @return Value that all visited atoms reduce to.
*/
public long reduce(int startAtomIndex, boolean stopAtParenClose) {
// Every occurence of atoms.remove() below is an instance of reduction.
int i;
Long prevValue = null;
Atom atom;
// Reduce parens via recursion
i = startAtomIndex - 1;
PAREN_SEEKER:
while (atoms.size() >= ++i) {
if (atoms.size() == i) {
if (stopAtParenClose) throw new IllegalStateException("Unbalanced '" + MathOp.LPAREN + "'");
break;
}
atom = atoms.get(i);
if (atom.op != null)
switch (atom.op) {
case RPAREN:
if (!stopAtParenClose)
throw new IllegalStateException("Unbalanced '" + MathOp.RPAREN + "'");
atoms.remove(i);
break PAREN_SEEKER;
case LPAREN: // Recurse. Reduction inside of reduce().
atoms.remove(i);
atoms.add(i, new Atom(reduce(i, true)));
break;
default:
// Intentionally empty
}
}
int remaining = i - startAtomIndex;
if (remaining < 1) throw new IllegalStateException("Empty expression");
// System.out.println("Need to consume " + remaining + " after parens removed");
Atom nextAtom;
MathOp op;
// Reduce powers
i = startAtomIndex;
atom = atoms.get(i);
if (atom.op != null)
throw new IllegalStateException(
"Expected initial value expected but got operation " + atom.op);
while (startAtomIndex + remaining > i + 1) {
if (startAtomIndex + remaining < i + 3)
throw new IllegalStateException("No operator/operand pairing remaining");
nextAtom = atoms.get(i + 1);
if (nextAtom.op == null)
throw new IllegalStateException("Operator expected but got value " + nextAtom.val);
op = nextAtom.op;
nextAtom = atoms.get(i + 2);
if (nextAtom.op != null)
throw new IllegalStateException("Value expected but got operator " + nextAtom.op);
if (op != MathOp.POWER) {
// Skip 'atom' (current) and the operand that we'll handle later
i += 2;
atom = nextAtom;
continue;
}
// Reduce the operator and right operand Atoms
remaining -= 2;
atoms.remove(i + 1);
atoms.remove(i + 1);
long origVal = atom.val;
atom.val = 1;
for (int j = 0; j < nextAtom.val; j++) atom.val *= origVal;
}
// Reduce multiplication and division
i = startAtomIndex;
atom = atoms.get(i);
if (atom.op != null)
throw new IllegalStateException(
"Expected initial value expected but got operation " + atom.op);
while (startAtomIndex + remaining > i + 1) {
if (startAtomIndex + remaining < i + 3)
throw new IllegalStateException("No operator/operand pairing remaining");
nextAtom = atoms.get(i + 1);
if (nextAtom.op == null)
throw new IllegalStateException("Operator expected but got value " + nextAtom.val);
op = nextAtom.op;
nextAtom = atoms.get(i + 2);
if (nextAtom.op != null)
throw new IllegalStateException("Value expected but got operator " + nextAtom.op);
if (op != MathOp.MULTIPLY && op != MathOp.DIVIDE && op != MathOp.REM) {
// Skip 'atom' (current) and the operand that we'll handle later
i += 2;
atom = nextAtom;
continue;
}
// Reduce the operator and right operand Atoms
remaining -= 2;
atoms.remove(i + 1);
atoms.remove(i + 1);
if (op == MathOp.MULTIPLY) atom.val *= nextAtom.val;
else if (op == MathOp.DIVIDE) atom.val /= nextAtom.val;
else atom.val %= nextAtom.val;
}
// Reduce addition and subtraction
// Reduce the leading value
atom = atoms.remove(startAtomIndex);
remaining--;
if (atom.op != null)
throw new IllegalStateException("Value expected but got operation " + atom.op);
long total = atom.val;
while (remaining > 0) {
// Reduce the operator Atom
--remaining;
atom = atoms.remove(startAtomIndex);
op = atom.op;
// System.err.println("Trying +/- for " + op);
if (op == null)
throw new IllegalStateException("Operator expected but got value " + atom.val);
if (remaining <= 0) throw new IllegalStateException("No operand for operator " + op);
// Reduce the right operand
--remaining;
atom = atoms.remove(startAtomIndex);
if (atom.op != null)
throw new IllegalStateException("Value expected but got operation " + atom.op);
switch (op) {
case ADD:
total += atom.val;
break;
case SUBTRACT:
total -= atom.val;
break;
default:
throw new IllegalStateException("Unknown operator: " + op);
}
}
return total;
}
