## Convert Input Field to Formula

0
Would there be a way to take an string input field with something like: 4 * 8 * 2 * 5 + 11 and do the math and return the correct result? If yes, I would also like to try adding a formula id to some of my table, then parse the use a Microflow to convert the id to a number. When all done I would pass the resulting string to the function that did the math. Is this possible?
0

Martin, compliments for getting this to work, but let me be the partypooper:

This and more is available in the marketplace module ‘Math’.

See https://mathenginetestapp-sandbox.mxapps.io/p/simple for a demo

0

I did find a java routine that says it would do what I want, how do I add this into my code.

public static double eval(final String str) {
return new Object() {
int pos = -1, ch;

void nextChar() {
ch = (++pos < str.length()) ? str.charAt(pos) : -1;
}

boolean eat(int charToEat) {
while (ch == ' ') nextChar();
if (ch == charToEat) {
nextChar();
return true;
}
return false;
}

double parse() {
nextChar();
double x = parseExpression();
if (pos < str.length()) throw new RuntimeException("Unexpected: " + (char)ch);
return x;
}

// Grammar:
// expression = term | expression `+` term | expression `-` term
// term = factor | term `*` factor | term `/` factor
// factor = `+` factor | `-` factor | `(` expression `)`
//        | number | functionName factor | factor `^` factor

double parseExpression() {
double x = parseTerm();
for (;;) {
if      (eat('+')) x += parseTerm(); // addition
else if (eat('-')) x -= parseTerm(); // subtraction
else return x;
}
}

double parseTerm() {
double x = parseFactor();
for (;;) {
if      (eat('*')) x *= parseFactor(); // multiplication
else if (eat('/')) x /= parseFactor(); // division
else return x;
}
}

double parseFactor() {
if (eat('+')) return parseFactor(); // unary plus
if (eat('-')) return -parseFactor(); // unary minus

double x;
int startPos = this.pos;
if (eat('(')) { // parentheses
x = parseExpression();
eat(')');
} else if ((ch >= '0' && ch <= '9') || ch == '.') { // numbers
while ((ch >= '0' && ch <= '9') || ch == '.') nextChar();
x = Double.parseDouble(str.substring(startPos, this.pos));
} else if (ch >= 'a' && ch <= 'z') { // functions
while (ch >= 'a' && ch <= 'z') nextChar();
String func = str.substring(startPos, this.pos);
x = parseFactor();
if (func.equals("sqrt")) x = Math.sqrt(x);
else if (func.equals("sin")) x = Math.sin(Math.toRadians(x));
else if (func.equals("cos")) x = Math.cos(Math.toRadians(x));
else if (func.equals("tan")) x = Math.tan(Math.toRadians(x));
else throw new RuntimeException("Unknown function: " + func);
} else {
throw new RuntimeException("Unexpected: " + (char)ch);
}

if (eat('^')) x = Math.pow(x, parseFactor()); // exponentiation

return x;
}
}.parse();
}