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Calculator 4

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1) The document provides instructions for coding a basic calculator app in LiveCode, including coding the equals button to perform calculations and updating variables to allow for continued use. 2) It describes adding code to handle new numbers, different math operators, and toggling between positive and negative values. Variables are used to track the current operation, total, and whether a new number is being entered. 3) The code examples show how to use if/else statements and switches to perform the correct calculation based on the current operator, then update the display and variables to allow for further input.

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Calculator Day 4 : Math Create It With in cooperation with 1
Calculator App Many of you are thinking - oh no not math. This is why I can never be a programmer because it is all about math, bit and bytes. Well the good news is, that LiveCode just makes it simple and easy. Today we will code the heart of the calculator app: Equals =. You are probably thinking that it only gets processed when the user presses the = button. But actually if you think about it, the calculator needs to total the number with every operation. How do you think we are going to do this? LiveCode + Math 2
Calculator App Yes, it is that simple. You will create your own equalsPressed command to do the calculations. But first, we need to get the code ready to calculations. The first issue we need to deal with is knowing when a number button is pressed, do we add it to the existing display or start a new number. We are going to need to create lNewNumber, a variable to keep track of this for us. Equals local lCurrentOperator. lNewNumber Remember that you have to Edit the Card Script, and go all the way to the top. 3
Calculator App lNewNumber will let us know if we should start with a new number. So the first place we need to code this is in the numberPressed command If you remember yesterday we did a quick if...then statement to check if the display value was 0. 1. You just need to change the code to if lNewNumber = true then 2. Then since it is not a new number anymore, you will need to put false into lNewNumber. lNewNumber on numberPressed pNumPress if the text of field "display" = "0" then if lNewNumber = true then ---just set the Display to the number pressed put pNumPress into field "display" put false into lNewNumber --Not a new Num anymore else ---add the pressed number to the display put pNumPress after field "display" End if end numberPressed 2 1 4
Note Calculator App Data Type and Auto Conversion LiveCode does differentiate between text and numbers. It will try and convert a variable as number if you use it as such. If the string is not numeric , LiveCode will generate an error. But if you look at the second block, the testNumber is actually a text variable of 5. LiveCode detects that it is a number and will convert it to a number for you. The third block of code sets testNumber as a number 5 and just does the math. put "five" into testNumber multiply testNumber by 3 -- An error will occur put "5" into testNumber multiply testNumber by 3 -- LiveCode will calculate 15 by converting 5 put 5 into testNumber multiply testNumber by 3 -- LiveCode will calculate 15 5
Calculator App It might look difficult, but it is as easy as 123. equalsPressed on equalsPressed --get out if no currentOperator, nothing to calculate if lCurrentOperator is empty then exit equalsPressed put field "display" into tCurrentValue switch lCurrentOperator case "/" put lCurrentTotal / tCurrentValue into lCurrentTotal break case "x" put lCurrentTotal * tCurrentValue into lCurrentTotal break case "-" put lCurrentTotal - tCurrentValue into lCurrentTotal break case "+" put lCurrentTotal + tCurrentValue into lCurrentTotal break end switch put lCurrentTotal into field "display" end equalsPressed 1 2 3 1. Put the value in the display into a temp variable tCurrentValue 2. Based on the current operator, LiveCode will select one of the four math calculation options. 3. Once the match is done, then show the new current total to the user in the display field. 6
Calculator App Now that we have finished the calculations, we need get ready for the user to enter in more numbers. We only have 2 more steps to make that happen. equalsPressed 1 2 1. We need to clear the operator by setting lCurrentOperator to empty and hiding the border on the button. 2. If the user starts to press another number, the code needs to know that it will be a new number. 3. Now we just add equalsPressed to on mouseUp of the = button. on equalsPressed .... put lCurrentTotal into field "display" ---Now that we performed the operation, clear it set the ShowBorder of button lCurrentOperator to false put empty into lCurrentOperator ---add the pressed number to the display put true into lNewNumber end equalsPressed on mouseUp equalsPressed end mouseUp 3 7
Calculator App We also need to add an update to lCurrentTotal to the end of these routines: operatorPressed percentPressed You can add this on the bottom of the commands. lNewNumber ---update the calculation variable put field "display" into lCurrentTotal 8
LiveCode follows standard mathematical order of operations. For example, in mathematics and most computer languages multiplication is done before addition; in the expression 2 + 3 4, the answer is 14. Brackets, "( .. )", which have their own rules, may be used to avoid confusion, thus the preceding expression may also be rendered 2 + (3 4). But is you did (2 + 3) 4 the answer would be 20. We recommend that you ALWAYS use brackets as much as possible to avoid any misconceptions. It is cleaner code and will help you avoid costly mistakes and bugs in the future. Check out the Wikipedia page for full details. Order of Operations Order of Operations Calculator App 9
Calculator App Lets finish with coding the togglePressed. The calculator uses the 賊 button to toggle the number in the display between positive and negative. Edit Card Script and create a new command togglePressed. The code is simple and straightforward. Then in call the command on mouseUp from the 賊 button on togglePressed on togglePressed ----just toggle between positive and negative put field "display" into tCurrentValue put tCurrentValue * -1 into field "display" put field "display" into lCurrentTotal end togglePressed on mouseUp togglePressed end mouseUp 10
If you wish to learn more Visit LiveCode Congrats on completing: Math Dont forget to save your LiveCode Project! Calculator App 11

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Calculator 4

  • 1. Calculator Day 4 : Math Create It With in cooperation with 1
  • 2. Calculator App Many of you are thinking - oh no not math. This is why I can never be a programmer because it is all about math, bit and bytes. Well the good news is, that LiveCode just makes it simple and easy. Today we will code the heart of the calculator app: Equals =. You are probably thinking that it only gets processed when the user presses the = button. But actually if you think about it, the calculator needs to total the number with every operation. How do you think we are going to do this? LiveCode + Math 2
  • 3. Calculator App Yes, it is that simple. You will create your own equalsPressed command to do the calculations. But first, we need to get the code ready to calculations. The first issue we need to deal with is knowing when a number button is pressed, do we add it to the existing display or start a new number. We are going to need to create lNewNumber, a variable to keep track of this for us. Equals local lCurrentOperator. lNewNumber Remember that you have to Edit the Card Script, and go all the way to the top. 3
  • 4. Calculator App lNewNumber will let us know if we should start with a new number. So the first place we need to code this is in the numberPressed command If you remember yesterday we did a quick if...then statement to check if the display value was 0. 1. You just need to change the code to if lNewNumber = true then 2. Then since it is not a new number anymore, you will need to put false into lNewNumber. lNewNumber on numberPressed pNumPress if the text of field "display" = "0" then if lNewNumber = true then ---just set the Display to the number pressed put pNumPress into field "display" put false into lNewNumber --Not a new Num anymore else ---add the pressed number to the display put pNumPress after field "display" End if end numberPressed 2 1 4
  • 5. Note Calculator App Data Type and Auto Conversion LiveCode does differentiate between text and numbers. It will try and convert a variable as number if you use it as such. If the string is not numeric , LiveCode will generate an error. But if you look at the second block, the testNumber is actually a text variable of 5. LiveCode detects that it is a number and will convert it to a number for you. The third block of code sets testNumber as a number 5 and just does the math. put "five" into testNumber multiply testNumber by 3 -- An error will occur put "5" into testNumber multiply testNumber by 3 -- LiveCode will calculate 15 by converting 5 put 5 into testNumber multiply testNumber by 3 -- LiveCode will calculate 15 5
  • 6. Calculator App It might look difficult, but it is as easy as 123. equalsPressed on equalsPressed --get out if no currentOperator, nothing to calculate if lCurrentOperator is empty then exit equalsPressed put field "display" into tCurrentValue switch lCurrentOperator case "/" put lCurrentTotal / tCurrentValue into lCurrentTotal break case "x" put lCurrentTotal * tCurrentValue into lCurrentTotal break case "-" put lCurrentTotal - tCurrentValue into lCurrentTotal break case "+" put lCurrentTotal + tCurrentValue into lCurrentTotal break end switch put lCurrentTotal into field "display" end equalsPressed 1 2 3 1. Put the value in the display into a temp variable tCurrentValue 2. Based on the current operator, LiveCode will select one of the four math calculation options. 3. Once the match is done, then show the new current total to the user in the display field. 6
  • 7. Calculator App Now that we have finished the calculations, we need get ready for the user to enter in more numbers. We only have 2 more steps to make that happen. equalsPressed 1 2 1. We need to clear the operator by setting lCurrentOperator to empty and hiding the border on the button. 2. If the user starts to press another number, the code needs to know that it will be a new number. 3. Now we just add equalsPressed to on mouseUp of the = button. on equalsPressed .... put lCurrentTotal into field "display" ---Now that we performed the operation, clear it set the ShowBorder of button lCurrentOperator to false put empty into lCurrentOperator ---add the pressed number to the display put true into lNewNumber end equalsPressed on mouseUp equalsPressed end mouseUp 3 7
  • 8. Calculator App We also need to add an update to lCurrentTotal to the end of these routines: operatorPressed percentPressed You can add this on the bottom of the commands. lNewNumber ---update the calculation variable put field "display" into lCurrentTotal 8
  • 9. LiveCode follows standard mathematical order of operations. For example, in mathematics and most computer languages multiplication is done before addition; in the expression 2 + 3 4, the answer is 14. Brackets, "( .. )", which have their own rules, may be used to avoid confusion, thus the preceding expression may also be rendered 2 + (3 4). But is you did (2 + 3) 4 the answer would be 20. We recommend that you ALWAYS use brackets as much as possible to avoid any misconceptions. It is cleaner code and will help you avoid costly mistakes and bugs in the future. Check out the Wikipedia page for full details. Order of Operations Order of Operations Calculator App 9
  • 10. Calculator App Lets finish with coding the togglePressed. The calculator uses the 賊 button to toggle the number in the display between positive and negative. Edit Card Script and create a new command togglePressed. The code is simple and straightforward. Then in call the command on mouseUp from the 賊 button on togglePressed on togglePressed ----just toggle between positive and negative put field "display" into tCurrentValue put tCurrentValue * -1 into field "display" put field "display" into lCurrentTotal end togglePressed on mouseUp togglePressed end mouseUp 10
  • 11. If you wish to learn more Visit LiveCode Congrats on completing: Math Dont forget to save your LiveCode Project! Calculator App 11