LOG10 Operator

[famer]

I am trying to parse an expression that has a logarithm as

expr = 10 * log10( 12345 / (  (5 ^ 2) * 3) )

Can this be done using JEP 2.4.1?

If not, can it be done using a later version of JEP?



-famer

[Richard Morris]

Jep uses "log" for the base 10 logarithm and "ln" for base e logarithm. So you can do

 
   expr = 10 * log( 12345 / (  (5 ^ 2) * 3) )

If you want to use "log10" for base 10 logs them you can change the name of the function using JEP.addFunction(String, PostfixMathCommandI).

Richard

[famer]

Thank you for the quick reply.

I tried to use it as "log" in my expression like you mentioned but I get the error "Syntax Error (implicit multiplication not enabled)".

This is how my parser has been set up
       
        org.nfunk.jep.JEP myParser = new org.nfunk.jep.JEP();
        myParser.setAllowUndeclared(true);
        Node node = jep.parseExpression(test);
        if ( jep.hasError()) {
            System.out.println("ERROR: " + jep.getErrorInfo());
        }

I can only make it work if I use a later version of JEP. I used the trial version 3.3.0 of the Jep parser as
       Jep jep = new Jep();
       Node node = jep.parse(test);
       com.singularsys.jep.walkers.TreeAnalyzer ta = new com.singularsys.jep.walkers.TreeAnalyzer(node);
       System.out.println(ta.toString());

Is it that version 2.4.1 does not support function parsing?

Thanks,
-F

[Richard Morris]

I'm not quite sure why you are getting problems. This code works for me

JEP myParser = new JEP();

myParser.addStandardFunctions();

myParser.parseExpression("10 * log( 12345 / (  (5 ^ 2) * 3) )");

System.out.println(myParser.getValue());

If you try and do

myParser.parseExpression("10 * log10( 12345 / (  (5 ^ 2) * 3) )");

Jep does not understand "log10" is a function and interprets it as "log * 10" using implicit multiplication. 

However unless you explicitly call myParser.setImplicitMul(true); it will not allow implicit multiplication and raise an exception.

On Thursday, 25 September 2014 01:02:39 UTC+1, famer wrote:

Thank you for the quick reply.

I tried to use it as "log" in my expression like you mentioned but I get the error "Syntax Error (implicit multiplication not enabled)".

This is how my parser has been set up
       
        org.nfunk.jep.JEP myParser = new org.nfunk.jep.JEP();
        myParser.setAllowUndeclared(true);
        Node node = jep.parseExpression(test);
        if ( jep.hasError()) {
            System.out.println("ERROR: " + jep.getErrorInfo());
        }

I can only make it work if I use a later version of JEP. I used the trial version 3.3.0 of the Jep parser as
       Jep jep = new Jep();
       Node node = jep.parse(test);
       com.singularsys.jep.walkers.TreeAnalyzer ta = new com.singularsys.jep.walkers.TreeAnalyzer(node);
       System.out.println(ta.toString());

Is it that version 2.4.1 does not support function parsing?

I'm not sure whats wrong with this code you would need to post the complete code.

Richard

[famer]

That was the problem...I was missing the "addStandardFunctions()" call. After adding this, the parsing is ok without errors. Thanks for the help.

On a different note, we were thinking of upgrading to JEP 3.4.0, but I encountered an issue while trying to use the addOperator api. OperatorKey does not seem to be defined anywhere in the jar file and the code would not compile. Version 3.3.0 does not have this issue. Is it better to upgrade to 3.3.0?

Thanks,
-F

[Richard Morris]

I would go with the 3.4.0 versions as it fixes a number of minor bugs with 3.3. I'm not quite sure what the problem with OperatorKey can you post an example?

Richard

[famer]

Actuallly I found that OperatorKey is somehow in the package OperatorTable2 although it is not shown. Thanks for all the input and help. Most probably we will upgrade to version 3.4.0.

Thanks,
-F

[famer]

So if we go to the "Order" page, and I want to get the latest jar (3.4) which item number should I select? Is it Item # 1059 (Jep Java 3.4   Binary).

Thanks,
-F

[Nathan Funk]

Yes that's correct

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