Check value statement

[MaxV]

Hi,
I'm working on a scientific calculator, and I'm using value like this:

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put value of "3+3" into myresult

If the string is not correct, like "oops+3+3", it crashes!
How can I test if the string is a valid script for value or for do functions?

[jmburnod]

Hi MaxV,

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put value of "3+3" into myresult

don't work for me
You have to change it to:

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put THE value of "3+3" into myresult

You can test if a string is a number like that:

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put isNumber("oops+3+3") return false

I hope this help
Best regards
Jean-Marc

[bn]

Hi Max,

(salut Jean-Marc)

As Jean-Marc said.

from the dictionary:

value

Type: function

Syntax:
the value of expression
value(expression[,object])

You have two ways to invoke a in-built function in Livecode. The "normal" way with parenthesis or "the value of xxx". In the second case you have to use "the" and "of" otherwise the compiler does not know what you mean.

here are some ways to add 2 numbers.

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on mouseUp
   put the value of "3+3" into field 1
   
   put cr & value("3+3") after field 1
   
   put cr & 3 + 3 after field 1
   
   put 3 into tVar1
   put 3 into tVar2
   put cr & tVar1 + tVar2 after field 1
   
   put cr & myAddingFunction(tVar1,tVar2) after field 1
   
   put cr & myAddingFunctionWithErrorChecking(tVar1, tVar2) after field 1
   
   put "oops" into tVar2
   put cr & myAddingFunctionWithErrorChecking(tVar1, tVar2) after field 1
end mouseUp

function myAddingFunction param1, param2
   return param1 + param2
end myAddingFunction

function myAddingFunctionWithErrorChecking param1, param2
   if not (param1 is a number) or not(param2 is a number) then return "error, must be numbers"
   return param1 + param2
end myAddingFunctionWithErrorChecking

put this into a button and make a field.

Kind regards
Bernd

[jmburnod]

Simple, clear, useful... Berndly

[MaxV]

Thank you very much jmburnod.
Now, I solved for my calculator, but is there a check or parse function that control if statement is correct?
I was used to work with Rebol language (very similar to LiveCode) and there was a try function that you could use this way:

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if  try (do "put 3 into b")
 then 
  do "put 3 into b" 
  else 
  answer "WRONG CODE"
 end if

Is there any similar in LiveCode?

[MaxV]

No, I didn't resolve even for my calculator:

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isNumber("3+3")

return false

I tried also:

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"3+3" is a number

but it returns false
Any suggestions?

[Klaus]

Hi Max,

why don't you take a look into the dictionary?
It ain't really THAT bad

Sure there is a "TRY" structure in Livecode, but is is not a function as in your Rebol example.

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...
  try
    do "put 3 into b"
    
    ## Catch possible error
  catch errornum
  ## ERROR happened!
  ## Now do what you need in this case
  answer "WRONG CODE!"

  ## Exit htis handler or do whatever you need
  exit HANDLER_NAME
  end try

  ## Success, cary on with your script...
...

Best

Klaus

[bn]

Hi Max,

if you code

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put value ("3+3") is a number

it returns TRUE

if you just put

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put "3+3" is a number

then it returns FALSE since it is in quotes which means in Livecode that it is a string/literal.

if you put

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put 3+3 is a number

then it returns TRUE since Livecode "sees" that it is numbers and does the right thing.

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isNumber(value("3+3"))

returns TRUE since you force the evaluation before passing the parameter to the function isNumber. Without evaluation first isNumber "thinks" it is a string literal because of the quotes, see above.

Kind regards
Bernd

[MaxV]

Hi Max,

why don't you take a look into the dictionary?
It ain't really THAT bad
...
Best

Klaus

Thank you Klaus!!! I searched try in the dictionary without finding it, but I found it in the User Guide! Yes!
I'll publish my scientific calculator very soon!
Thank you, thank you, thank you, thank you!

[Klaus]

Hm, it IS in fact in my dictionary...

[jacque]

Also, I'd avoid the "vaule" or "do" functions here. They both have some overhead because the engine needs to load the compiler every time either one is used, and LiveCode syntax makes them unnecessary most of the time. The examples Bernd gave that don't use "value" or "do" will work fine.

There are very few cases where scripts need those functions, the engine is pretty smart.