checking input

[ethanCodes]

How would I check the user input to make sure it is a number and not a letter or something else? I used if else statements to check to make sure the input is within the desired range, but I'm unsure of how to check for letters.

[dunbarx]

Hi,

If you mean user entry into a field, put this into the field script

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on keyDown tKey
   if tKey is in "0123456789." then pass keyDown 
end keyDown

Now this is deceptively simple looking, but contains within it several key foundational tenets of LC. What do you think these might be?

Craig Newman

[ethanCodes]

I have no idea. I know so little about LC that I wouldn't even know what to guess. I don't understand how this language doesn't have data types. It seems like this would limit the language so much.

[ethanCodes]

also, why do people prefix variables with letters? and how do you decide which letter to prefix. eg your example, tkey

[Simon]

Here is Richard's excellent post on naming conventions
http://fourthworld.com/embassy/articles ... style.html

Simon

[FourthWorld]

I don't understand how this language doesn't have data types. It seems like this would limit the language so much.

The data types are there; what's absent is the tedium of having to manually declare and coerce them.

When we write:

put field 1 + field 2 into field 3

...LiveCode is smart enough to see that we're doing arithmetic so it automatically coerces the display strings from the field structures to numbers, and when we put the result into the third field it knows the field structure needs a string so it converts it for us.

Handy stuff, all taken care of for us so we can focus on crafting the user experience and leave the tedious bit counting to machines

[dunbarx]

Ethan.

What Richard said.

Another way to look at it is that LC types its variables based purely on context. If you try to:

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add 3 to horse

you will get a runTime error if horse does not contain a number. But you will not get a compileTime error, since the context has not yet been determined. I am not conversant with strongly typed languages, but would such a statement, or its syntactic equal, get even that far?

You have no idea, as Richard alluded to, how liberating this is. Maybe you will shortly. The question you must ask yourself is simple: can LC accomplish what you need? I guarantee it offers sufficient power and range.

Craig Newman

[jacque]

How would I check the user input to make sure it is a number

Due to LiveCode's English-like syntax you answered your own question:

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if it is a number then...  

In some cases it's better to iterate the integers like Craig did, but in this case you can probably just use the built-in method.

See "is a" in the dictionary, there are many types you can check for.

[ethanCodes]

Thank you for all the replies. You all helped me understand more of the different parts of LC. I'm getting a better understanding of it.