Re: Evaluate basic arithmatic in a string
From: David Morris (dmorris_at_dynamicquest.com)
Date: 04/02/04
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Date: Fri, 02 Apr 2004 10:48:20 -0500 To: Mykola Rabchevskiy <chief@ockhamstyle.com>
Ok, this is an excellent suggestion to start solving the problem.
I have coded your suggestion, sort of.
To do this, correct me if I am wrong, I will still need 5 conditional
tests to hardwire the coding for each restriction level one I decide
which one to use.
I can almost accept that to simple do the casting. However, then I need
to do the evaluation. In the case I gave you is "+=". It could be any
arithmetic function ( a + b / d * c ).
Can I then run a common method to do the evaluation whatever the type
is? I can parse through and set a, b, c, and d to the same type based
on the functionality you have already provided. But how can I
generically to math against the values regardless of their type?
Thanks again for the help.
Mykola Rabchevskiy wrote:
> Order types by restriction level:
>
> type: double float long int short
> level: 0 1 2 3 4
>
> and cast operand with have higher level to type of lover level,
> then perform operation using two operands with same types.
>
>
> David Morris wrote:
>
>> OK, this is for you experienced Java programmers out there.
>>
>> I have a string that contains the following value:
>>
>> "myValue += 5"
>>
>> I need, in Java, to be able to evaluate this expression.
>>
>> Caviots:
>> myValue can be int, float, long, double, or short.
>>
>> Likewise, the 5 could also be a variable of any of the above listed
>> types. ie, "myValue += myValue2".
>>
>> Just so you know the environment, I an writing a java scripting
>> janguage where I can have a user build a template on the fly and I
>> interpret all the java code manually. I am about 75% finished
>> mimicing the JVM in the scripting but am lacking basic math functions.
>>
>> I use a class
>>
>> class ObjDef {
>> Object value;
>> Class className;
>> }
>>
>> to store and pass values throughout the script interpretation process.
>>
>> so I know the value and class of myValue and myValue2 and I know to
>> cast 5 to an int if not otherwise set.
>>
>> The real caviot comes in that if myValue is an int, the className in
>> ObjDef is int but the Object is Integer.
>>
>> How do I get myValue ( which is really ObjDef.value ) to an int so I
>> can do an actully myValue = myValue + 5 and put it back in the ObjDef
>> class?
>>
>> Realize if I do a hard cast, 25 different possible combinations (5^2),
>> so I am looking for a different answer.
>>
>> Thank you for any help you can offer.
>>
>
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