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I want to find some solution that can solve expression like this
(98.83*(a1^3))-(89127*a1)-53480000 = 0
a1 ^ 3 = cos(a1) / (279 ^ 2) - 0.30293
I want to know value of a1
- The expression have a1 variable.
- a1 can has more than one time in expression.
- a1 can in left side and right side.
I searched by uses keywords "expression solver" then I found many solutions but they aren't match
my requirements
many solution can find result of expression e.g 2 ^ 5 + (300 * 4)
by use stack,prefix,postfix
but I not found a solution that can find variable value.
if you have any solution even it isn't use vb.net please help me.
or may be you suggest me to use other keywords for search actually I don't know what a keyword i should use because my English skill isn't well.
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Hi,
seems to me you need two things:
1. some code that evaluates an expression such as
y = (98.83*(a1^3))-(89127*a1)-53480000
or y = a1 ^ 3 - cos(a1) / (279 ^ 2) + 0.30293
for a specific value of a1
2. some code that finds the zeroes of y(a1), i.e. those values of a1 for which
y effectively becomes zero.
You can do 1. the lazy way by editing it into a source file, i.e. make a specific
program. Or you need a parser + expression evaluator, which have been handled
in several CP articles.
You can do 2. using a simple algorithm, I would suggest "Newton-Raphson" which
basically says: for a given approximation x to the solution,
x - y(x)/y'(x) is a better approximation.
Here y' is the derivative, which you can obtain in two ways:
- you could come up with its analytical form and add it to the source code as suchl
or you could do it symbolically by writing a parser + derivative generator,
I don't recall having seen one on CP yet.
- and you could approximate y'(x) by calculating y(x) and y(x+dx) and
setting y'(x)=(y(x+dx)-y(x))/dx which may be a good enough approximation
for small dx.
Warning: if you come up with an arbitrary expression in a1, there could be
zero, one, two, or any number of solutions. Since iterative approaches need
an initial guess, they tend to converge (at best) to one or a few of the solutions,
there is no easy way to find all solutions.
Warning2: Newton-Raphson may not converge at all, if your initial guess is
far away from a real solution but close to a local minimum/maximum, it may just
move and stay there.
Warning3: you will need defensive programming to protect yourself against
overflow, underflow, zero divide, and non-convergence.
There are some web sites that solve simple equations for you, and even tell
you how they do it. I don't remember having seen solutions for trig equations.
quadratics[^]
Newton[^]
Luc Pattyn [Forum Guidelines] [My Articles]
This month's tips:
- before you ask a question here, search CodeProject, then Google;
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get;
- use PRE tags to preserve formatting when showing multi-line code snippets.
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Thank you for your reply.It can help me a lot.
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you're welcome.
Luc Pattyn [Forum Guidelines] [My Articles]
This month's tips:
- before you ask a question here, search CodeProject, then Google;
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get;
- use PRE tags to preserve formatting when showing multi-line code snippets.
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System results in NOT RESPONDING state.
I want to have an infinite loop till end button is pressed. Through looping, I want to monitor few files. I used if, for, do, while, until , but none of them resulted in a fruitful way. Can anyone plz help me how I can achieve such looping. Plz help with examples.
Thanks in advance.
My code can be viewed here: http://www.codeproject.com/script/Forums/View.aspx?fid=1646&msg=2467756[^]
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arp_059 wrote: I want to have an infinite loop till end button is pressed
Then the loop must go on a different thread. If you loop infinitely then your application will not know about the button press because it is too busy looping to handle events.
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doesn't application.doevents check if anything else has happened/being pressed etc. I've used it before to put an exit function in a loop from a stop button.
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The ANZAC wrote: doesn't application.doevents check if anything else has happened/being pressed etc. I've used it before to put an exit function in a loop from a stop button.
Yes, but you could end up in some terrible recursion problems if you are not careful. The recommended way is to use separate threads.
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yeh i'm in agreeance, it really depends on the scale of your application too.
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You can create a defacto infinite loop with the timer control. Just drag and drop it into your project and when you set the enable property to true it generates an event periodically. You can then write code in that event to check your file. When you want to stop checking then set the enable property to false.
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How about using Timer control? Not so professional but still it gets the job done.
- Stop thinking in terms of limitations and start thinking in terms of possibilities -
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Hiii..,,,
Keep "Application.doevents" in your infinite loop. then Try.
Thanks
Rajesh B
Rajesh B --> A Poor Workman Blames His Tools <--
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Unless you're REALLY careful about what you're doing, using "DoEvents" in a workaround like this is a dangerous thing to do, causing some very difficult bugs to work out.
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Hi ,
i took datetimepicker its format is dd-MMM-yyyy
Command.Parameters.Add("@DOB", SqlDbType.DateTime, 50).Value = Format(dtpCustDOB.Value, "YYYY-MM-DD")
i am getting "Failed to convert parameter value from a String to a DateTime
Kindly suggest.
i tried with cdate
Thanks.
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soniasan wrote: Command.Parameters.Add("@DOB", SqlDbType.DateTime, 50).Value = Format(dtpCustDOB.Value, "YYYY-MM-DD")
i am getting "Failed to convert parameter value from a String to a DateTime
The errors suggests that you pass a DateTime object. So, why are you converting the DateTime object the Date Time picker gave you in to a string first?
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it is necessary to create DSN for using crystal report.
without using DSN we can create a crystal report.
i want to generate a dynamic crystal report from visual basic 6.0 and backend used is oracle.
i tried it but giving error like 'server not yet been started'.
i don't know TSNname for oracle.
give me reply.
if possible then a code for generating dyanamic report. with backend oracle assume i don't create any report file. from the first step. i just install vb and oracle with user name "dtbs" password "dtbs".
please help me.
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You have 2 major problems.
1 You are using a development platform 6 years out of date (VB6) and therefore the support level will be low (and skills thankfully forgotten)
2 You are attempting to use Crystal Reports, note there is no forum for CR because it is a PITA.
How does you app get at the database?
I used to build CR based on stored procs and a connection string but you can also use datasets passed from your application. If you cannot talk to the database you have a serious problem.
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OK, so I have a very basic application for a client that, right now, simply connects to a device, K8055. The application references a DLL, k8055d.dll, which is in the root directory of the project.
On application start-up, the device is connected to using the OpenDevice() function in the DLL file, which is precessed in a separate thread. Appropriate information, for example, if the application is unable to connect, is reported back to the end user.
In short, the application is connecting everytime the device is attached to the computer, and when it is not, this is reported back to the user. But there is a problem: when closing the form (not exiting the application), the following error occurs:
Title: [AppName].vshost.exe - Application Error
The exception unknown software exception (0x0eedfade) occured in the appication at location 0x7c812a5b
A further message appears, citing runtime error 217 at 00009C34.
The project compiles without any errors or warnings, and due to this, am beginning to think it is due to the DLL file, k8055d.dll. I have no suggestion and to how to fix this, and would like some help!? Please ... ?
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Your best source of information on this is going to be whoever wrote that library. With the information you've given, there's really nothing telling us what could be wrong.
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I am basically an electronics student. I am currently developing a vb code to control multiple devices using bluetooth. I am making use of vb here. I am a very beginner in vb and dont have much knowledge. Please help me with examples.
Problem:
Below, I have provided the code which I developed for my project. It monitors few text files located in C:\ directory and based on that, the relevant code is sent through parallel port which I use to further purposes.
The problem occurred that I need to monitor those files. I used loop, do, if, goto, while statements. Till the end button is pressed, it needs to monitor the existence of files.
All the statements resulted in "NOT RESPONDING" state. Can anyone please help me for that. I just want my program to loop continuously from end to beginning till the end button(command2) is pressed. Then I used a check button and used if command, it also did not work.
Here is the code I wrote till now
-----------------------------------
Private Sub Command1_Click()<br />
' following sections to read file line obtained from http://www.codeguru.com/forum/archive/index.php/t-315872.html<br />
Dim strFile As String<br />
Dim PortAddress As Integer<br />
'Dim iFile As Integer<br />
Dim strContent As String<br />
Dim strContent2 As String<br />
Dim strContent3 As String<br />
Dim strContent4 As String<br />
PortAddress = &H378<br />
'TO Do Add code here to put a filename with path in strFile<br />
Label1.Caption = "light is off" 'display status<br />
Label3.Caption = "fan is off" 'display status<br />
<br />
file1 = "c:\lighton.txt"<br />
file2 = "c:\lightoff.txt"<br />
file3 = "c:\fanon.txt"<br />
file4 = "c:\fanoff.txt"<br />
'iFile = FreeFile '1=lighton.txt 2=lightoff.txt 3=fanon.txt 4=fanoff.txt<br />
'restart:<br />
Do<br />
<br />
If (Len(Dir$(file1)) <> 0) Then 'lighton.txt file existance check<br />
For j = 1 To 255<br />
Close #j<br />
Next j<br />
Open "c:\lighton.txt" For Input As #1<br />
'The following will read the first line from the file<br />
Line Input #1, strContent ' read 1st line in the file<br />
Close #1 ' close file<br />
If (strContent = "light on") Then 'check validity of file<br />
Label1.Caption = "light is on" 'display status<br />
Value = Inp(PortAddress)<br />
Value = Value Or &HF 'make lsbs high<br />
Out PortAddress, Value 'output the value<br />
End If<br />
For i = 1 To 5<br />
If (Len(Dir$(file2)) <> 0) Then 'lighton.txt file existance check<br />
For j = 1 To 255<br />
Close #j<br />
Next j<br />
Open "c:\lightoff.txt" For Input As #2<br />
'The following will read the first line from the file<br />
Line Input #2, strContent2 ' read 1st line in the file<br />
Close #2 ' close file<br />
If (strContent2 = "light off") Then 'check validity of file<br />
Label1.Caption = "light is off" 'display status<br />
Value = Inp(PortAddress)<br />
Value = Value And &HF0 'make lsbs high<br />
Out PortAddress, Value 'output the value<br />
Kill "c:\lighton.txt"<br />
Kill "c:\lightoff.txt"<br />
End If<br />
End If<br />
Next i<br />
<br />
End If<br />
<br />
<br />
<br />
' monitor for fan files<br />
<br />
If (Len(Dir$(file3)) <> 0) Then 'lighton.txt file existance check<br />
For j = 1 To 255<br />
Close #j<br />
Next j<br />
Open "c:\fanon.txt" For Input As #3<br />
'The following will read the first line from the file<br />
Line Input #3, strContent3 ' read 1st line in the file<br />
Close #3 ' close file<br />
If (strContent3 = "fan on") Then 'check validity of file<br />
Label3.Caption = "fan is on" 'display status<br />
Value = Inp(PortAddress)<br />
Value = Value Or &HF0 'make lsbs high<br />
Out PortAddress, Value 'output the value<br />
End If<br />
For i = 1 To 5<br />
If (Len(Dir$(file4)) <> 0) Then 'lighton.txt file existance check<br />
For j = 1 To 255<br />
Close #j<br />
Next j<br />
Open "c:\fanoff.txt" For Input As #4<br />
'The following will read the first line from the file<br />
Line Input #4, strContent4 ' read 1st line in the file<br />
Close #4 ' close file<br />
If (strContent4 = "fan off") Then 'check validity of file<br />
Label3.Caption = "fan is off" 'display status<br />
Value = Inp(PortAddress)<br />
Value = Value And &HF 'make lsbs high<br />
Out PortAddress, Value 'output the value<br />
Kill "c:\fanon.txt"<br />
Kill "c:\fanoff.txt"<br />
End If<br />
End If<br />
Next i<br />
<br />
End If<br />
<br />
<br />
<br />
'Sleep 1000 'Implements a 1 second delay<br />
<br />
<br />
<br />
Loop Until ((Check1.Value = 0))<br />
<br />
'GoTo restart<br />
<br />
End Sub<br />
<br />
Private Sub Command2_Click()<br />
End<br />
End Sub<br />
<br />
<br />
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Take a look at the FileWatcher class (I think) this works for small file numbers (chokes when there are too many events.
Also you should change your loop to a timer based application, something like
Start time
Timer tick event
Turn timer off
Process directory
turn timer on
Set the tick for 1 second
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Wow, this is some old code. Warning - This code will NOT work with VB.NET and won't work at all under a Windows NT Kernel O/S, such as WIndows 2000, XP, 2003, Vista, ...
What version of Basic is this and what O/S are you planning on running it under?
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Hi Guys,
Im trying to build a stock system for a small cd store, iv got the basics out the way, but i need help with something a bit more complex.
The form i need to build will need to show the weekly sales for each product. The way id imagine i would build was to have a data table with the products down the side of the table and the dates ( 11/03/08 - 12/03/08 - 13/03/08 etc.) at the top. The information in the table will hold the quantity sold for that day. Everytime a sale is processed the qty will be updated on this table.
Does anybody have any idea how i could go about bulding this?
I appreciate any help i get.
Thanks
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The logical way to do this is to have a table that logs each sale, with it's date, and you write SQL queries that build reports from that data. If the table knows when each CD was sold, then you can report on that any way you like.
Christian Graus - Microsoft MVP - C++
"also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )
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I found nice example how to draw lines by mouse on form. I want to have picture as background and write lines on this picture. Is there anyone who can show me how can I put picture as background?
Imports System.Windows.Forms
Public Class frmIceTimeShots
' True while we are drawing the new line.
Private m_Drawing As Boolean
' Buffer for erasing rubberband lines.
Private m_BufferBitmap As Bitmap
Private m_BufferGraphics As Graphics
' The mouse position.
Private m_X1 As Integer
Private m_Y1 As Integer
Private m_X2 As Integer
Private m_Y2 As Integer
Private Sub SaveSnapshot()
Dim new_bitmap As Bitmap
' Make a new bitmap that fits the form.
new_bitmap = New Bitmap(Me.Width, Me.Height)
m_BufferGraphics = Graphics.FromImage(new_bitmap)
' Clear the new bitmap.
m_BufferGraphics.Clear(Me.BackColor)
m_BufferGraphics.DrawImage(new_bitmap, 0, 0)
' Copy the existing bitmap's contents into
' the new bitmap.
If Not (m_BufferBitmap Is Nothing) Then
m_BufferGraphics.DrawImage(m_BufferBitmap, 0, 0)
End If
' Save the new bitmap and graphics objects.
m_BufferBitmap = new_bitmap
End Sub
' Continue drawing the rubberband line.
Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e _
As System.Windows.Forms.MouseEventArgs) Handles _
MyBase.MouseMove
' Do nothing if we're not drawing.
If Not m_Drawing Then Exit Sub
' Save the new point.
m_X2 = e.X
m_Y2 = e.Y
' Erase the previous line.
DrawForm(Me.CreateGraphics())
' Draw the new line directly on the form.
Me.CreateGraphics().DrawLine( _
Pens.Gray, m_X1, m_Y1, m_X2, m_Y2)
End Sub
' Redraw the saved buffer.
Private Sub DrawForm(ByVal gr As Graphics)
If Not (m_BufferBitmap Is Nothing) Then _
gr.DrawImage(m_BufferBitmap, 0, 0)
End Sub
Private Sub frmIceTimeShots_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
' Do nothing if this isn't the left mouse button.
If e.Button <> MouseButtons.Left Then Exit Sub
m_Drawing = True
' Save a snapshot of the form.
SaveSnapshot()
' Save the current mouse position.
m_X1 = e.X
m_X2 = e.X
m_Y1 = e.Y
m_Y2 = e.Y
End Sub
' Finish drawing the new line.
Private Sub Form1_MouseUp(ByVal sender As Object, ByVal e _
As System.Windows.Forms.MouseEventArgs) Handles _
MyBase.MouseUp
' Do nothing if we're not drawing.
If Not m_Drawing Then Exit Sub
m_Drawing = False
' Save the new point.
m_X2 = e.X
m_Y2 = e.Y
' Draw the new line permanently on the buffer.
m_BufferGraphics.DrawLine( _
Pens.Blue, m_X1, m_Y1, m_X2, m_Y2)
' Redraw to show the new line.
DrawForm(Me.CreateGraphics())
End Sub
' Redraw the form.
Private Sub Form1_Paint(ByVal sender As Object, ByVal e As _
System.Windows.Forms.PaintEventArgs) Handles _
MyBase.Paint
DrawForm(e.Graphics)
End Sub
End Class
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