From b453ec0047b5a87e36098b3519e085f03d917d81 Mon Sep 17 00:00:00 2001
From: Ben Culkin <scorpress@gmail.com>
Date: Sat, 28 Mar 2020 12:02:32 -0400
Subject: Add DualExprParser

This class parses DualExprs from prefix expressions
---
 .../main/java/bjc/utils/math/DualExprParser.java   | 200 +++++++++++++++++++++
 1 file changed, 200 insertions(+)
 create mode 100644 base/src/main/java/bjc/utils/math/DualExprParser.java

(limited to 'base/src/main/java/bjc/utils/math/DualExprParser.java')

diff --git a/base/src/main/java/bjc/utils/math/DualExprParser.java b/base/src/main/java/bjc/utils/math/DualExprParser.java
new file mode 100644
index 0000000..71d62c7
--- /dev/null
+++ b/base/src/main/java/bjc/utils/math/DualExprParser.java
@@ -0,0 +1,200 @@
+/**
+ * 
+ */
+package bjc.utils.math;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import bjc.utils.esodata.SimpleStack;
+import bjc.utils.esodata.Stack;
+import bjc.utils.esodata.Stack.StackUnderflowException;
+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 {
+	public static class Result {
+		public DualExpr expr;
+		public Map<String, DualExpr> varMap;
+
+		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.
+	 *
+	 * @param preVars Any pre-existing variables to use.
+	 * 
+	 * @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 StackUnderflowException 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;
+	}
+}
\ No newline at end of file
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