Eval simple expressions

I need to provide dynamic evaluation of simple expressions from within an application, and don't want to re-invent the wheel by implementing yet another expression language. I wish Java had a package for dynamic evaluation of simple expressions (can't believe it doesn't), but javascript expressions would be just fine., so I"ve been looking into that.
Unfortunately, the "obvious" javascript eval function made available to Java (in JSObject) seems to require an Applet within a browser context. (I'm sorry, are applets the only place where javascript is useful???)
Anyway, can anyone suggest how to eval javascript expressions, or suggest an alternative language whose expressions can be evaluated from Java code without too much effort. I don't need to use javascript -- just thought it was a no-brainer until I started trying to actually do it.

JFormula is a complete evaluation system working with various types (string,double,bigdecimal,boolean...). You can use if/then/else expression and
plug your functions or operators...
http://www.japisoft.com/formula/index.html

Similar Messages

RDLC report fails to build simple expression

Hi,
I have a very curious case. I've just downloaded a solution in VS2010 SP1. Everything builds fine except a single RDLC report which fails with a cryptic error:
Error 17 An unexpected error occurred while compiling expressions. Native compiler return value: ‘-1073741515’.
Looking at report definition I deleted all report items except a textbox with below definition
<TextRuns>
<TextRun>
<Value>=Parameters!ReportTitle.Value</Value>
<Style>
<FontSize>16pt</FontSize>
<FontWeight>Bold</FontWeight>
<Color>Navy</Color>
</Style>
</TextRun>
</TextRuns>
If I simply replace "=Parameters!ReportTitle.Value" for "abc" the project builds fine.
The mentioned parameter has a default value.
Any clue why my VS2010 Ultimate SP1 doesn't like to build this simple expression, other devs can build it fine.
Thanks,
Lucas

Hi HGG42,
Per my understanding that you got the error about using this expression "=Parameters!ReportTitle.Value" in the Textbox when creating the RDLC report, right?
As you have mentioned that that the parameter have a default value, i would like to know if you have check "Allow Multiple values", if you have check this, you will got some errors, you can uncheck this or you can modify the expression in the textbox
as:" =join(Parameters!ReportTitle.Value,",") "
If you haven't check the "Allow Multiple values", the issue can be caused by uthentication problem, please check your application's (if ASP) UserName and Password provided in your service.
Similar thread below for your reference:
http://www.c-sharpcorner.com/forums/thread/234749/rdlc-unexpected-error-occurred-while-compiling-expression.aspx
http://forums.asp.net/t/1923313.aspx?Native+compiler+error+1073741502+
If you still have any problem, please feel free to ask.
Regards
Vicky Liu

Simple expression evaluator

Hi all,
need some help with an expression evaluation:
user inputs a string like "x*x+dx*dy" or "x*dx-y*dy" and I
would like Flash to covert this to an actionscriptline so in the
code it appears like:
x=3;
dx=0.6;
dy=0.1;
aa=x*x+dx*dy;
trace(aa);
and the output would be: 9.06
Now my problem is converting the operator.
Anybody for a solution for this newbie?
thnx
Rob

Ok, so I think my advice stands then...
You could write your own expression parser, using eval("x")
when you came to parse an x in the string etc...and its probably
not too complicated to do if you're just dealing with
multiplication and addition.... or you could use existing code like
the example in the link I posted earlier to parse the expression
(I've used that code before for something more complex).
If you were writing your own parser you could use eval("x")
...but if it were me... I would do the opposite. That is to split
and join the string with the variable names, subsitituting their
values into the string and then run it through that expression
parser. Its basically just calculating a string version of a
numeric expression then with no variables.
For your variable --> value substitution (split and then
join) you need to do it in the order of the
dx and dy
then x and y
so you get it to work correctly.

Problem with simple expression

Hi,
I have an SSRS report based on a SSAS cube that contains a Date field called Closing_Date.
This field can be null in the database.
The purpose is to convert the DateTime into a Date field respecting the user's locale
This expresion returns a blank for empty dates and a DateTime (yyyy/mm/dd hh:mm:ss) for non empty dates
=Fields!Closing_Date.Value,DateFormat.ShortDate
This expression returns OK for non empty dates and NOK for empty dates
=IIF(Trim(Cstr(Fields!Closing_Date.Value)) <> "","OK","NOK")
However this expression returns an #error for all empty dates. I don't understand because he should just return NOK.
Why would a change in the True part if the IIF give a different result if the date is empty.
=IIF(Trim(Cstr(Fields!Closing_Date.Value)) <> "",FormatDateTime(Fields!Closing_Date.Value,DateFormat.ShortDate),"NOK")
I get this error in the VS.Net Conversion from string "" to type 'Date' is not valid
Any Idea's?
PS : Other date fields (that don't contain null's) work correctly and can be converted with FormatDateTime function
Regards,
Sven Peeters

Hi Sven,
According to your description, when you iif function to set empty dates to NOK when you preview the report, the error occurred: Conversion from string "" to type 'Date' is not valid. But the fields with data can be converted successfully.
I reproduced the issue in my local machine, the error is caused by data type. I suppose the data type of Closing_Date is string, so when we tried to convert a string with null data, the error occurred. To achieve your goal, please use the expression like
below:
=IIF(Fields!Closing_Date.Value = "", "NOK" , FormatDateTime(IIf(Fields!Closing_Date.Value = "" , Nothing , Fields!Closing_Date.Value) , DateFormat.ShortDate))
If you have any more questions, please feel free to ask.
Thanks,
Wendy Fu

"Eval Parsed Formula Node VI" does not return outputs in predefined order

I make a data analysis program, where the data consists of some million events and each event has e.g. 4 channels and 1-5 hits on each channel.
I would like the user to select different expressions of these channels to give coordinates to plot in a 2D histogram (increment a bin in Intensity Graph), e.g. for some experiment you want to show x=ch1-ch2; y=ch1+ch2+ch3+ch4; while in another experiment you want x=ch1-123; y=123-ch2;
There are other VIs that use static LabView-code for the normal things, but now after a few years of adding to this program I find that it would be quite good with a general plotter and let the user specify simple expressions like this. Also with the "normal" static plots, there is a need to filter out bad data and then it would be much simpler both to program and use if you could write text expressions with boolean logic to combine multiple filters. Making a LabView code and GUI that allows AND/OR/parenthesis combinations of expressions will be quite an effort and not very reusable.
So, with the above motivation, I hope you see that it would make sense to have a useable string formula evaluator in LabView. I find some info about MathScript's user-defineable functions, but haven't managed to get MathScript working in LV2010 yet (maybe some licensing or installation issues, I think I had it in 8.6). But I think it would be possible to do most of what I want for the display-part (not the filtering) with the simpler Eval/Parse Formula Node VIs and suitable use of the limited variable name space. So I started testing, and found a quite annoying issue with how the evaulator works.
To the parser, you are expected to send an array of output variable names. But then it ignores this array, and returns one output per assignment/semicolon in the formula, in the order of the formula text. Since the static parts of my program need to know what the output values mean (which of them is x and which is y), I would have to rely on the user not using any intermediate variable and defining x before y. The attached screenshot demonstrates the problem, and also that it has been solved by NI statff in the "Eval Formula Node VI" which does the appropriate array-searching to extract only the pre-defined outputs, in their expected order. But using that VI is about 100 times as slow, I need to pre-compile the formula and then only use the evaulator in the loop that runs over a million events.
I don't know if I'll take the time to make my own tweks to the parsing stage (e.g. preparation of array-mapping to not have to repeat the search or maybe hacking the output list generated by the parser) or if I'll have to make it in a static Formula Node in the block-diagram (which supports more functions), so that the user has to run with development environment and stop the program to change the plotting function. But I wanted to share this trouble with you, in hope of improvments in future LabView versions or ideas from other people on how I could accomplish my aim. I have MATLAB-formula node possibility too, but is far as I have seen the only place the user could update the formula would then be in a separate .m file, which is re-read only when typing "clear functions" in the Matlab console window. (Having this window is also an annoyance, and perhaps the performance of calling Matlab in every iteration is not great.)
Besides this issue, it also seems very strange there is virtually no support for conditional expressions or operators in Formula Node evaulated formulas (called Mathematics VIs in the documentation). Maybe using (1+sign(a-b))/2 you can build something that is 0 when a<b and 1 when a>b, but it is not user friendly! Would it really be diffcult to add a function like iif(condition, return_value_if_true, return_value_if_false) to replace the unsupported "condition ? if_true : if_false" operator? Would it really be difficult to add support for the < <= >= > == || && operators? Although compiled to an assemply language, this can't exactly be difficult for a CPU.
Attachments:
LV script test.png ‏62 KB
LV script test.vi ‏18 KB

(1) You can put any kind of code inside an event structure with the limitation that it should be able to complete quickly and without user interaction. For example a while loop for a newton-raphson method is fine, but an interactive while loop where the stop condition depends on user iteraction is not recommended. By default, event structures lock the front panel until the event completes, so you would not even be able to stop it.
(2) Yes, you can do all that. LabVIEW has no limitation as a programming language. Use shift registers to hold data and state information, the manipulate the contents as needed.
(3) I would recommend to use plain LabVIEW primitives instead of formula nodes. Show us your code so we can better see what it's all about. Obviously you have a mismatch betweeen scalars and arrays. It is impossible from the given information where the problem is.
(4) Yes, look inside the nonlinear curve fit VI (you can open it an inspect the code!). One of the subVIs does exactly that. Just supply your model VI.
LabVIEW Champion . Do more with less code and in less time .

Urgent help needed in building an expression

hi,
I am using expression editor to build the following simple expression.
"if inputvalue = 0 then 10 else 20"
so Far I have used various forms of "IF" and "CASE" statements but could not successfully create the expression.Could not find anything useful in the help docs as well.
any help asap would be highly appreciated..highly disappointed with OWB which does not allow to build such a simple expression and the user docs as well are very poor.

Hi,
There is something you need to know up front on expressions and transformations. Expressions are SQL expressions, whereas transformations are pl/sql.
Looking at your pseudo code, you are trying to do a procedural thing. So there are 2 ways of doing this. One is correctly the case statement. For an example on how to do this go to the OWB sample code page on OTN (http://otn.oracle.com/sample_code/products/warehouse/content.html) where an explanation is given on how to do this. It includes an example metadata file for you to evaluate.
The other way of doing this is in PL/SQL, in which case you would create a small function accepting in parameter and then doing the procedural language on that. To create this use the create functions activity in OWB. Here you will get a nice code editor (similar to the expression builder) to guide you in the creation of this function.
Hope this helps,
Jean-Pierre

Help- WDS with Extreme-N & 2x Airport Express with ~ 40% packet loss

So this problem is driving me crazy. I recently moved into a house that has enough metal in the walls (don't ask) to prevent me from using a single base station so I expanded my network as a WDS utilizing an Airport Extreme (mixed NGB mode) and two Airport Express (one as a relay and one as remote). The configuration appears to work normally some times but other times (especially evenings) I get a very high rate of dropped packets between the client notes (which are connected through the WDS-enabled Expresses) and the base station (using a simple ping 10.0.1.1 to check connectivity to the APBS-N). The problem manifests itself from a users' perspective as very long DNS lookups which causes slow page loads in a browser but it's very reproducible via ping.
So far I've tried changing the channels on the network but I haven't seen a huge payoff there. iStumbler reports no additional networks on channel 2 which I'm using, there are some on channel 1, 5, and 13. I've also tried channels 7 and 11. We have no microwave in the house and our cordless phone (5.8ghz) never interrupted with our simpler Express-based network at our old house, n/m the fact that the phone is never in use when we have this problem.
I don't seem to see the problem when I'm local to (in the same room as) the AEBS; it really seems to happen only when I'm on the WDS-enabled remote and/or relay.
Other data points that may help are that the AEBS-N drops out of the Airport utility at the same time. Sometimes isn't gone for 30 seconds, other times for > 30 minutes. The other base stations continue to report "Green" in that they are not having any WDS problems. If I disconnect the remote node the relay will correctly reflect a status of yellow, so I know it somewhat works.
It's an open network (no encryption, open SSID) so it's unlikely that there's an issue there.
Clients include an Apple TV, iBook G4, MacBook, Tivo Series 3, Intel Mini and Dell Latitude D810. Because of the diversity of clients I don't think it's a driver or NIC adapter issue on any of the clients.
Does anyone have any experience working in a similar environment? Suggestions on troubleshooting packet loss (or other performance issues) in a WDS network?
Thanks,
Mike

Hello errorsupply. Welcome to the Apple Discussions!
I suggest downloading a copy of iStumbler. Use iStumbler's Inspector feature (select Edit > Inspector from iStumbler's menu) to determine the Signal-to-Noise Ratio (SNR) at different points around your house, by performing a simple RF site survey. Within the Inspector, note the values for "signal" & "noise" at these locations. Start with your MacBook near the main base station, note the readings, and then, choose the locations where you have the relay and remote base stations.
SNR is the signal level (in dBm) minus the noise level (in dBm). For example, a signal level of -53dBm measured near an access point and typical noise level of -90dBm yields a SNR of 37dB, a healthy value for wireless LANs.
The SNR, as measured from the MacBook, decreases as the range to the base station increases because of applicable free space loss. Also an increase in RF interference from microwave ovens and cordless phones, which increases the noise level, also decreases SNR.
SNR Guideline
o 40dB+ SNR = Excellent signal
o 25dB to 40dB SNR = Very good signal
o 15dB to 25dB SNR = Low signal
o 10dB to 15dB SNR = Very low signal
o 5dB to 10dB SNR = No signal
If the SNR is 20dB+ at each of these locations, then you should be getting reasonable performance from your AirPorts. If less, either try to locate/eliminate the source of the Wi-Fi interference or try relocating the relay and/or remote base station until they are within a 20dB SNR range of the main (and for the remote, of the relay).

Difference between regular expressions and spry character masking?

Hi,
This is my first time writing my own regular expressions. Often times though, they seem to work in various testing widgets, but then they do not perform as expected in Spry. I have no idea how to even begin to debug this.
For example, this string:
^\#?[A-Fa-f0-9]{3}([A-Fa-f0-9]{3})?$
Does a perfect job enforcing hex colors in a regexp testing widget. But it doesn't work in spry. It won't let me type a darn thing in.
Can somebody throw me a bone here?

Hi!
Thank you for the response. I read that article prior to posting and it seems to relate more to Spry's custom pattern function rather than regular expressions. Here's the code I have:
<script type="text/javascript">
     
</script>
Expected behavior: I should be able to type in a valid hex color and have Spry perform validation.
Actual behavior: I can't type anything in, at all. I immediately get the invalid Spry feedback (in my case a little red .png image and an error message).
Simpler expressions like this work fine in Spry:
                    <script type="text/javascript">
     
</script>
I think if I can figure out what the special rules are for one somewhat robust regular expression in Spry, then I will be off and running.
Can anyone help?
Scott

If expressions

How do I create an expression if I want to return a value if another value is > or < a set value? For example:
if ( Subtotal < 25.00 ) then
ShippingCharge = 6.00
elseif ( Subtotal > 25.01 or < 50.00) then
ShippingCharge = 8.00
elseif ( Subtotal > 50.01 or < 75.00) then
ShippingCharge = 10.00
endif
I know this is not the correct syntax but it illustrates what I'm trying to accomplish.

The syntax is listed in the "Scripting Reference" under LiveCycle Designer's menu "Help" option.
if ( simple expression ) then
list of expressions
elseif ( simple expression ) then
list of expressions
else
list of expressions
endif
There are also examples available.
You could also use JavaScript and the "switch{case():...}" statement. Wich might more clearly state and test the comparisons.
What is the shipping charge if the Subtotal is $25.00, $25.01, $50.00 or $50.01? You have to be careful with the end points of ranges.

Dynamically parent two layers together with expressions

In AECS6, I have an Image Layer that is using the layer directly above as a Alpha Matte. I want both layers to scale at the same time, unless a certain condition is setup where I only want the matte to scale - leaving the image at original size. Normally I'd just make a new pair of layers and only scale that, but ALL my layers are dynamically linked to eachother for another more complex effect.
I wrote a simple expression to get the current scale of the matte layer (index-1), and then calculate what this particular layer's scale should be. But the scales don't match up just right because we are dealing with percentages... not absolute values. However, if I simply parent the two layers together, it of course works.
So, I either need to find a way to turn the parenting on/off with code, like if THIS, then ParentTo(index-1), or I need to write my scaling script correctly.
Fwiw- here's that script:
if (index != 15)) {
// get the original and current scale value of the layer just above, and calculate an offset
          sOrig = thisComp.layer(index-1).transform.scale.valueAtTime(0)[0];
          sNow = thisComp.layer(index-1).transform.scale[0];
          sOffset = value[0] + (sNow - sOrig);
          [sOffset,sOffset]
} else {
// this is layer index 15, don't do anything with it
          value;
Appreciate the help!

Not sure what you are getting at, but the actual value ranges do not really matter in an expression. It's more likely you are eitehr having an anchor point issue or your keyframes are simply not linear. in the latter case of course a simple subtraction would not give the correct result because values would be exponential/logarithmic/whatever. You'd have to use much more complex code then to accumulate all values over time such as the great Dan Ebberts explains on his website:
http://www.motionscript.com/articles/speed-control.html
Anyway, I suppose you could always use effects rather than native transforms to scale your matte while still leaving it parented. Y' know, there is a Transform effect... That would be much simpler and also avoid the expression evaluation bogging down your system...
Mylenium

Expressions in PS?

Is there a way to add simple expressions to Photoshop?
In After Effects when you put "287/11" as a value, it automatically divides it for you.
Can Photoshop do that and how?

No, Photoshop does not do that.

Expression Issues

Hi All,
I am trying to do what I thought was a relativly simple expression but after litterally hours and serveral variations I am no further forward.
Essentially I have 2 objects; 1 null and 1 graphic - both 2D.
The graphic moves vertically controlled by a combination of keyframes (to gradually move it from the top to the bottom of the comp) and a wiggle expression (in turn controlled by a slider) to make its movement more turbulent.
[value[0],wiggle(1,effect("Slider Control")("Slider"))[1]]
This all works fine.
What I am trying to do is make the null stay at the lowest y position the graphic has reached - should almost look like the graphic is pushing the null down by jumping on it.
The expression I have is this:
a = thisComp.layer("Graphic1").transform.position[0];
b = thisComp.layer("Graphic1").transform.position[1];
v=value[0];
w=value[1];
if(b>w){
w=value[1];
[v,b]
}else{
[v,w]
It sort of works - the null stays attached to Graphic1 but wont go above its start position.
What I think is going wrong is that w doesnt update itself so it is stuck at its first frame position and ignores the new y position (gennerated by the wiggle expression).
Unfortunatly I can just keyframe this and re-structure using pre-comps as this is only a small part of a much bigger beast that uses aroun 50 elements all using various elements.
Thanks for your help

Not sure what you are hoping to achieve. In your case w is defined as value[1], which is the property base value - before any expressions. Naturally it never changes and your expression is therefore useless. Anyway, your simplitic code can't achieve what you want. You need to construct a while() loop and accumulate values with valueAtTime() or something like that or as a minor do something with Math.max() to return only the largest possible value at a given time. There's enouzgh examples on Dan Ebberts' site, but it's not gonna be your usual Andrew Kramer 5 second expression...
Mylenium

Expression request

I've been askjing around to find out how a particular effect that I seen on numerous music video was created. No one could give me definitive answer, I even suggested maybe it was done by editing in Premiere, which others agreed is a strong possibility. However to hold this effect for a long period of time or to try different layer stacking would be very tedious in an editing program.
The effect here http://youtu.be/T6j4f8cHBIM   at 0:50       or        http://www.vevo.com/watch/nicki-minaj/stupid-hoe-explicit/USCMV1100087
I was given a wiggle expression        wiggle(1,50) < 50 ? 0 : 100         that makes a layer's opacity either 0 or 100 if the wiggle value is above or below a defined number, but the result of this is random.
I've never written my own expression and I've discovered even trying to verbalize the desired action and result takes very presice language, so here's my attempt.
I would like to control a layer's ocacity by having it alternate, in sequential order, through a complete cycle of assigned values x times per second.
ie.
Layer A opacity values = 0, 25,50,100 played in sequecial order at x frequency
I would like to use this expression to have layers that are stacked visable as follows:
(The start time of each layer is the same and the frequency rate in the expression the same).
Layer A opacity values = 100, 0, 0
Layer B opacity values = 0, 100, 0
Layer C opacity values = 0, 0, 100
With the expression applied to each layer, the visual result in the Comp window would be seeing Layer A,B,C in that order x times per second.   By having the expression reference a sequence of numbers I can choose to have 3 or 20 layers be totally, partially or invisible in a predictable/rhythmic way.
Thanks in Advance

You can do this using a few keyframes and a very simple expression.
On layer one, set an opacity keyframe at frame 0 to 100%. Make a hold keyframe, and then on the next frame set the opacity to zero, which should default to hold also. Finally on the third frame* set the opacity back to 100%. Alt-click on the stopwatch and add the expression loopOut(type='cycle');
Copy your keyframes and the expression to your other layers, and offset all the keyframes by one frame each layer, so on the second layer the first keyframe is on frame one, the third layer frame two, etc.
* Obviously this frame depends on how many layers you want to cycle through. Here we have three layers so the final keyframe setting the opacity back to 100 is on frame three (assuming your comp starts at frame zero). If you have 10 layers, this will be frame 10.
Hope that helps.
Christian

Algorithm for Expression Evaluator

Hi,
Can any one help me in finding out the algo of Expression Evaluator,Changing Pre fix to Post Fix and vise versa.
Tx in advance.
from
gomes_deb

There is a math expression parser at http://www.bestcode.com. It forms a tree structure where nodes are operators, functions, variables, numbers. Each node of the tree has children (for example parameters of a function are it's children in this tree). So, if you have a "x+sin(y)", the tree is like this:
___+
_x sin
_______y
Then when it is time to evaluate, you set the values of X and Y and call evaluate() method and it tells you what the result is.
The java bean is called JbcParser. It's features are:
*Easy to use, simple class API.
*Comes with predefined functions.
*Users can create custom functions/variables.
*Optimization: Constant expression elimination for repeated tasks.
Analytical Operators: +, -, /, , ^(power)
*Logical Operators: =(equals),&(and),|(or),!(not), <>(not equals), <=(less than or equals), >=(greater than or equals)
*Paranthesis: (, {, [
*Functions in the form of: f(x, y, z, ...)
*Function parameters are not calculated until needed.
*List of predefined functions is available in the documentation.
*Java source code is included.
An example of a simple expression is : LN(X)+SIN(10/2-5)
When parsed, this expression will be represented as: since the SIN(10/2-5) is in fact SIN(0) which is a constant and is 0.
Thus, in a loop, if you change the value of X and ask for the value of the expression, it will be evaluated quite fast since SIN(10/2-5) is not dependent on X.
X and Y are predefined variables. You can create your own variables as needed.
There are many predefined mathematical functions. They are listed in documentation. You can create your functions as needed. IF logic is implemented through a predefined IF(A,B,C) function. Similar logical functions can be created as needed.
It is located at: http://www.bestcode.com/html/jbcparser.html

10GR2 - No Validation Message in Expression

Hi
While using 10GR2, sometimes when I try to validate an expression, I don't get
any message in the 'Validation Results' box.
I have to quit out of OWB and log back in then try again. When I validate again I get the 'Validation Successful' message.
This is happening frequently for no apparent reason.
Is anyone else experiencing this or know what causes it?
Thanks
GB

There is some OWB Releases that this feature simply does not work.
I was using OWB 9.2.0.3. The validation for a simple expression, such as a SUBSTR, takes a really long time and fails with this wierd sdk.whatever... message. Replaced with OWB 10.1.0.2.0 and now I don't have this issue anymore. However, it still takes long time to validate simple expressions.....
Don't know if there's a patch for that, I never worried about it since OWB validation messages doesn't necessarily reflects problems in the app's you've developed.
Regards,
Marcos

Eval simple expressions

Similar Messages

Maybe you are looking for