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/**
*
*/
package bjc.utils.math;
import java.util.HashMap;
import java.util.Map;
import bjc.esodata.SimpleStack;
import bjc.esodata.Stack;
import bjc.esodata.Stack.StackUnderflow;
import bjc.utils.exceptions.InvalidToken;
import bjc.utils.exceptions.NonConstantPower;
import bjc.utils.exceptions.OperandsRemaining;
import bjc.utils.math.DualExpr.ExprType;
/**
* Create DualExprs from strings.
*
* @author Ben Culkin
*
*/
public class DualExprParser {
/**
* Result class from parsing exprs.
*
* @author Ben Culkin
*
*/
public static class Result {
/**
* The resulting expression.
*/
public DualExpr expr;
/**
* Any variables we found in the expression.
*/
public Map<String, DualExpr> varMap;
/**
* Create a new result.
*/
public Result() {
this.varMap = new HashMap<>();
}
}
/**
* Parses a dual expression from a postfix expression string.
*
* @param expr
* The string to parse the dual expression from.
*
* @return Both the parsed expression, and a map of all the variables used
*/
public static Result parseExpression(String expr) {
return parseExpression(expr, null);
}
/**
* Parses a dual expression from a postfix expression string.
*
* @param expr
* The string to parse the dual expression from.
*
* @param preVars
* Any pre-existing variables to use.
*
* @return Both the parsed expression, and a map of all the variables used
*
* @throws StackUnderflow
* If the expression is not properly formatted.
*/
public static Result parseExpression(String expr, Map<String, DualExpr> preVars) {
Result res = new Result();
if (preVars == null) {
} else {
res.varMap = preVars;
}
Map<String, DualExpr> vars = res.varMap;
String[] tokens = expr.split(" ");
Stack<DualExpr> exprStack = new SimpleStack<>();
for (int idx = 0; idx < tokens.length; idx++) {
String token = tokens[idx];
switch (token) {
case "add":
case "+": {
DualExpr rhs = exprStack.pop();
DualExpr lhs = exprStack.pop();
exprStack.push(new DualExpr(ExprType.ADDITION, lhs, rhs));
break;
}
case "subtract":
case "-": {
DualExpr rhs = exprStack.pop();
DualExpr lhs = exprStack.pop();
exprStack.push(new DualExpr(ExprType.SUBTRACTION, lhs, rhs));
break;
}
case "multiply":
case "*": {
DualExpr rhs = exprStack.pop();
DualExpr lhs = exprStack.pop();
exprStack.push(new DualExpr(ExprType.MULTIPLICATION, lhs, rhs));
break;
}
case "divide":
case "/": {
DualExpr rhs = exprStack.pop();
DualExpr lhs = exprStack.pop();
exprStack.push(new DualExpr(ExprType.DIVISION, lhs, rhs));
break;
}
case "abs": {
DualExpr opr = exprStack.pop();
exprStack.push(new DualExpr(ExprType.ABSOLUTE, opr));
break;
}
case "log": {
DualExpr opr = exprStack.pop();
exprStack.push(new DualExpr(ExprType.LOGARITHM, opr));
break;
}
case "sin": {
DualExpr opr = exprStack.pop();
exprStack.push(new DualExpr(ExprType.SIN, opr));
break;
}
case "cos": {
DualExpr opr = exprStack.pop();
exprStack.push(new DualExpr(ExprType.COS, opr));
break;
}
case "exp": {
DualExpr opr = exprStack.pop();
exprStack.push(new DualExpr(ExprType.EXPONENTIAL, opr));
break;
}
case "pow": {
DualExpr pow = exprStack.pop();
DualExpr bod = exprStack.pop();
{
Dual val = pow.number;
if (val.dual != 0)
throw new NonConstantPower();
}
exprStack.push(new DualExpr(ExprType.POWER, bod, pow));
break;
}
case "eval": {
DualExpr exp = exprStack.pop();
exprStack.push(new DualExpr(exp.evaluate()));
break;
}
case "dual": {
DualExpr dual = exprStack.pop();
DualExpr real = exprStack.pop();
exprStack.push(new DualExpr(
new Dual(real.evaluate().real, dual.evaluate().real)));
break;
}
default:
if (token.matches("[a-zA-Z][a-zA-Z0-9]*")) {
if (vars.containsKey(token)) {
exprStack.push(vars.get(token));
} else {
Dual var = new Dual();
DualExpr varExpr = new DualExpr(var);
vars.put(token, varExpr);
exprStack.push(varExpr);
}
} else {
try {
double d = Double.parseDouble(token);
exprStack.push(new DualExpr(new Dual(d)));
} catch (NumberFormatException nfex) {
throw new InvalidToken(token);
}
}
break;
}
}
if (res.expr == null) {
res.expr = exprStack.pop();
}
if (exprStack.size() > 0)
throw new OperandsRemaining(String.format(
"After processing expression, not all values had been consumed.\n\tRemaining values are '%s'",
exprStack.toString()));
return res;
}
}
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