Is there a method that allows me to evaluate a mathematical expression in a string? Example (Not actual Code):
Input = "2+2"
Output = SomeMethod(Input)
Output = 4
Update: Nevermind, I found a way around it by using DataTable.Compute.
You'll need a math expression parser to handle this.
Here are some various open source options on CodePlex:
Simple Math Parser
Fast Lightweight Expression Evaluator
ILCalc
A search will find many others...
Related
I am load testing an application that has a link that looks like this:
https://example.com/myapp/table?qid=1434e99d-5b7c-4e74-b64e-c24e9564514d&rsid=5c94ddc7-e2e4-4e69-8547-49572486f4d1
I need to get the dynamic value of the rsid so I can use it later in my script.
So far I have tried using the regex extractor and I am probably doing it wrong.
I have tried things like:
name = myvar
regular expression = rsid=(.*?) # didnt work
regular expression = <a href=".*?rsid=(.*?)"> # didnt work
Template = $1$
I have one extractor set up to get the csrf value and that one works as expected but that is also because the csrf value is in the page source.
The above link is NOT in the page source as far as I can see but it DOES show up when I inspect the link. I dont know if that is obfuscation or something else?
How can I extract the value of the rsid? Is the regular expression extractor the right one to use for this?
Should I be using something else?
Is it just a formula issue?
Thanks in advance.
Try something like:
rsid=[0-9A-Fa-f\-]{36}
the above regular expression should match a GUID-like structure and your rsid seems to be an instance of it.
Demo:
Also be aware of the Boundary Extractor, it's sufficient to specify "left" and "right" boundaries and it will extract everything in-between. In general coming up with "boundaries" is much easier than creating a regular expression, it's more readable and JMeter processes the Boundary Extractors much faster. More information: The Boundary Extractor vs. the Regular Expression Extractor in JMeter
I am trying to evaluate the following expression:
7088.800/(((((((24.65995+24.43061+24.54517+24.65192)/4)-32.0)*5/9)+273.15)/288.15)^.5)
If you are asking yourself why I didn't use Sqrt() instead of ^0.5 it's because I'm doing some things with the string beforehand that require there be no letters.
I am using this simple code:
Expression.CacheEnabled = False
x = New Expression(xEquation)
y = New Expression(yEquation)
System.Diagnostics.Debug.Write(x.Error)
System.Diagnostics.Debug.Write(y.Error)
Return New PointF(x.Evaluate, y.Evaluate)
The answer I get is: 7088.800
The correct answer is:7336.46922305(according to google)
I am using .net 3.5 and ncalc 1.3.8
I suspect it doesn't like the amount of brackets there are but I can't find any mention of that being a problem anywhere...
Thanks!
I cannot get Ncalc or Ncalc-edge (v1.4.1) to use the exponentiation operator ^ and produce the correct result. E.g., "4 ^ 2" gives 6. It does not accept ** as an operator.
A little bit of investigation shows that it uses ^ as the Xor operator, in the style of C#. C# does not have an exponentiation operator, so you will have to devise a way of parsing your actual input string and using Sqrt.
There are currently were some requests on the Ncalc discussion forum regarding this, such as Override ^ operator (link now dead, and it's not even available on the Wayback Machine).
I'm starting to study ANTLR.
The aim is to 'translate' Strings into SQL statements.
One simple example of what I want to do:
If I receive the String "name = A and age = B" --- ANTLR ---> "select * from USERS where name = 'A' and age = 'B'"
I've been reading some information about ANTLR, and following some examples, but those just convert the input stream of characters (source file) into a AST. But how can I use ANTLR to translate the input message, and use the translated output?
Can you give me some highlights or tell me where can I found some information about that?
I'm using the Eclipse IDE and Maven ANTLR Plugin.
ANTLR is just a parser generator. You can insert actions into the grammar that collect information or directly print output. The most common mechanism is to allow ANTLR to create an intermediate presentation in the form of an AST or, with ANTLR 4, a parse tree. From there, you build a tree walker to either build an internal model or directly generate output. From the internal model, which represent constructs in your output language, you can then generate the output. I typically use StringTemplate for generating structured text.
When the input and output are very similar and, more importantly, the order of output is very similar, you can get away with syntax directed translation: i.e. actions directly in the grammar or actions applied directly to a parse tree.
When the order of output is very different, you have to build some form of intermediate representation. Imagine simply reading in a bunch of integers and printing them back out in reverse order. You can do that by simply printing out the numbers as you see them. This is all explained in my [shameless plug] book, Language Implementation Patterns: Create Your Own Domain-Specific and General Programming Languages http://amzn.com/B00A376HGG
I am trying to format some output in Standard ML. I need to display some real values as rounded to a certain decimal place, and I also need to be able to display some real values using scientific notation.
The signature for the print function is
val it = fn : string -> unit
which doesn't seem to allow for the use of formatting codes or any other parameters. I also haven't had any luck finding documentation online. Ideally I was hoping the print function in SML would have similar functionality to printf in C...
Standard ML is a statically-typed language. It's hard to make something like printf in a type-safe way.
The SML Basis Library contains some formatting operations for numbers. But to use them is relatively verbose and relatively difficult to figure out. For example, to format a real number into a string in scientific notation with 3 places after the decimal point, you can do something like this:
Real.fmt (StringCvt.SCI (SOME 3)) 4324423423.5; (* evaluates to string "4.324E9" *)
Ugly, right?
Some implementations offer other formatting methods. For example, SML/NJ has a Format structure that allows you to use a printf-style formatting string. However, the arguments must be wrapped according to their type:
Format.format "%.3e" [Format.REAL 4324423423.5]; (* evaluates to string "4.324e09" *)
Other SML implementations might have their own custom formatting functions.
Is it possible to do String comparison where one of the strings I am comparing against has wild cards and is generally just for formatting purposes. For example
Dim correctFormat as String = "##-##-###-##"
Dim stringToCheck = someClass.SomeFunctionThatReturnsAStringToCheck
If FormatOf(CorrectFormat) = FormatOF(StringToCheck) then
Else
End if
I am aware of the made up FormatOf syntax, but I'm just using it to show what I am asking.
No need for regular expressions.
You can simply use the Like operator, which supports ?, * and # as wildcards and also character lists ([...], [!...])
So you simply change your code to:
If stringToCheck Like correctFormat Then
and it will work as expected.
The way is to use regular expressions - that's what they are for.
This is the regular expression that matches the format you have posted:
^\d{2}-\d{2}-\d{3}-\d{2}$
As the previous post mentioned, you should use regular expressions for that purpose - they are way better for that task.
Sadly, learning them can be confusing, especially finding bugs can be really annoying.
I really like http://www.regular-expressions.info/ and http://regexpal.com/ for building and testing regexes before.
In VB.net use something like reg.ismatch