### Inputting a Equation in Textfield and Processing it? [actionscript 3.0]

1

I would like to know if theirs a way where you can type in a text field something like "5*5".

And then on enter, the document would take the database and be able to return 25.

I am quite confused due to the fact that content that you input into a textfield must be a `String` and when you use the `Number()` converter the system gets confused.

2012-04-03 23:19
by Cyrus Kafai Wu
You can parse the string and look for operators like + - * and / and then perform the correct operation on the numbers on either side of those operators - M. Laing 2012-04-04 00:11

1

You'll need to break your string apart at operators (using regex) and then keep those operators.

I don't have the patience to do this myself but you'll need to prioritise certain operations as well (multiplication before addition, etc).

I've done some code to get you started - note that it only works with really simple algorithms in its current form:

``````// Finds +, - and *.
var operators:RegExp = /\+|\-|\*/g;
var numbers:RegExp = /\d+/g;

/**
* Attempts to work with a mathematical formula provided as string.
* @param str Subject string.
*/
function work(str:String):Number
{
var ops:Array = str.match(operators);   // List of operators in order.
var nums:Array = str.match(numbers);    // List of numbers in order.

var command:Array = [];
var cmbLen:int = Math.max(ops.length, nums.length);

for(var i:int = 0; i < cmbLen; i++)
{
if(nums[i]) command.push(nums[i]);
if(ops[i]) command.push(ops[i]);
}

// Begin performing the command.
var val:Number = 0;
var queuedOperator:String = "";

for(i = 0; i < command.length; i++)
{
// Apply initial value;
if(i == 0)
val = Number(command[i]);

// Work.
if(i % 2 == 0)
{
var num:Number = Number(command[i]);

// Operate if required.
if(queuedOperator.length > 0)
{
switch(queuedOperator)
{
case "+": val += num; break;
case "-": val -= num; break;
case "*": val *= num; break;
}
}

queuedOperator = command[i + 1] as String || "";
}
}

return val;
}
``````

And some testing:

``````trace(work("7 + 10")); // 17
trace(work("5 * 5")); // 25
trace(work("12 - 4")); // 8

trace(work("10 + 5 + 1")); // 16
``````

Feel free to build on this to include more operators (just add them into `operators`) and sort the `command` in order of priority. Adding `()` parenthesis will start to get interesting but with time I'm sure it's possible to get working right.

2012-04-04 00:43
by Marty

0

Here's another solution using RegExp. This can calculate whole and decimal numbers using the following signs: `^`,`%`,`/`,`*`,`+`,`-`. You can also use parantheses e.g. `2^(10/(2+3-2))`.

You will need to select the disable keyboard shortcuts option from the control menu when in test movie mode to see the result.

``````import flash.text.TextField;
import flash.text.TextFieldType;
import flash.text.TextFormat;
import flash.text.TextFieldAutoSize;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;

var tf:TextField = new TextField();
tf.defaultTextFormat = new TextFormat('_sans',24);
tf.autoSize = TextFieldAutoSize.LEFT;
tf.wordWrap = true;
tf.type = TextFieldType.INPUT;
tf.border = true;
tf.x = (stage.stageWidth - 300) * .5;
tf.y = 100;
tf.width = 200;
stage.focus = tf;

function tfKeyDown(e:KeyboardEvent):void {
if (e.keyCode == Keyboard.ENTER) {
e.preventDefault();
trace('Input:',tf.text);
trace('Result:',calculate(tf.text,7));
trace('-----------------------');
}
}

function calculate(str:String,maxDecimalCount:int=int.MAX_VALUE):Number {

var num:String = '-?[0-9]*\\.?[0-9]+';
var numRX:RegExp = new RegExp(num,'g');
var rx:RegExp, i:int;

// normalize minuses and eliminate spaces
str = str.replace(/--/g,'+').replace(/\s/g,'');

// calculate parenthesized equations
while (/\(([^\(\)]+)\)/.test(str)) {
str = str.replace(/\(([^\(\)]+)\)/g,function() {
return calculate(String(arguments[1]),int.MAX_VALUE).toString();
});
}

// exponential --> x^y
rx = new RegExp(num+'(\\^'+num+')+','g');
str = str.replace(rx,function() {
var nums = String(arguments[0]).match(numRX);
var res:Number = Math.pow(Number(nums[0]),Number(nums[1]));
for (i = 2; i < nums.length; i++) res = Math.pow(res,Number(nums[i]));
//trace('^ ['+nums+'] =',res);
return res;
});
// modulus --> x%y
rx = new RegExp(num+'(%'+num+')+','g');
str = str.replace(rx,function() {
var nums = String(arguments[0]).match(numRX);
var res:Number = Number(nums[0]);
for (i = 1; i < nums.length; i++) res %= Number(nums[i]);
//trace('% ['+nums+'] =',res);
return res;
});
// divide --> x/y
rx = new RegExp(num+'(/'+num+')+','g');
str = str.replace(rx,function() {
var nums = String(arguments[0]).match(numRX);
var res:Number = Number(nums[0]);
for (i = 1; i < nums.length; i++) res /= Number(nums[i]);
//trace('/ ['+nums+'] =',res);
return res;
});
// multiply --> x*y
rx = new RegExp(num+'(\\*'+num+')+','g');
str = str.replace(rx,function() {
var nums = String(arguments[0]).match(numRX);
var res:Number = Number(nums[0]);
for (i = 1; i < nums.length; i++) res *= Number(nums[i]);
//trace('* ['+nums+'] =',res);
return res;
});
// add or subtract --> x+y or x-y
rx = new RegExp(num+'([\\+\\-]'+num+')+','g');
str = str.replace(rx,function() {
var nums = String(arguments[0]).match(numRX);
var res:Number = Number(nums[0]);
for (i = 1; i < nums.length; i++) res += Number(nums[i]);
//trace('+- ['+nums+'] =',res);
return res;
});

var res:Number = Number(str);
// if the result is not a number...
if (isNaN(res)) {
throw new Error('Please input a valid equation using numbers and the following signs: ()^%/*+-');
}
// if the remainder needs to be shortened...
if (maxDecimalCount < int.MAX_VALUE &&
int(res) != res && String(res).split('.')[1].length > maxDecimalCount) {
res = Math.round(res * Math.pow(10,maxDecimalCount)) / Math.pow(10,maxDecimalCount);
}
return res;

}
``````
2012-04-04 03:10
by inhan
I'm not sure where modulus and exponential should be in the order, though. That might need a change - inhan 2012-04-05 12:48