How to change the value of a variable

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Posted: 4th Jun 2014 09:35

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Hi all! How to change the value of a variable? For example:
_start=1
...........
...........
do
..........
..........
if mouseclick()=1
........
_start=_start+1
........
endif
loop

its wrong
how to make?
Thanks

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VisualProg

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Posted: 4th Jun 2014 14:49 Edited at: 4th Jun 2014 14:50

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use tag "code"

public variable:

+ Code Snippet

local start

or

+ Code Snippet

global start

(is welcome write type)

+ Code Snippet

local start as integer

next, you do use your code:

+ Code Snippet

local start as integer
start=1

do

if mouseclick()=1

 start=start+1 ` or "inc start"

endif

set cursor 0,0
print "start="+str$(start)

loop

MZh[NUL] <---

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Green Gandalf

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Posted: 4th Jun 2014 16:37

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I didn't understand that answer.

The problem is that the loop is scanned several times while the mouse click still records 1 so your variable gets incremented several times for each mouse click.

There are at least two ways of dealing with that. The "quick and dirty" solution is to add a short loop which waits for the last mouse click to clear. For example

+ Code Snippet

_start=1
 do
   if mouseclick()=1
     _start=_start+1
     print _start
   endif
   while mouseclick() = 1 ` this waits for the mouse click to clear
   endwhile
 loop

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TheComet

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Posted: 4th Jun 2014 16:51 Edited at: 4th Jun 2014 17:36

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The not so dirty way is to process the mouse click to trigger on positive edges only. That way, program flow continues uninterrupted.

+ Code Snippet

global mouse_positive_edge as boolean
global mouse_last_state

_start=1
do
    process_mouse()

    if mouse_positive_edge = 1
        _start=_start+1
        print _start
    endif

loop

function process_mouse()
    mouse_positive_edge = (mouseclick()..7)&&mouse_last_state
    mouse_last_state = mouseclick()
endfunction

This also works when checking for right clicks and middle clicks, just test if mouse_positive_edge = 2. or if mouse_positive_edge = 4 respectively.

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Green Gandalf

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Posted: 4th Jun 2014 17:03 Edited at: 4th Jun 2014 17:09

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Doesn't compile.

Edit Neat - with typo fixed.

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    mouse_positive_edge = (mouseclick()..7)&&mouse_last_state

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TheComet

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Posted: 4th Jun 2014 17:35 Edited at: 4th Jun 2014 17:35

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Fixed. Thanks GG! I'm too used to C++

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Zero G Scott

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Posted: 4th Jun 2014 20:10

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What's a mouse positive edge? This sounds suspiciously handy if it means what I think it means.

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Green Gandalf

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Posted: 4th Jun 2014 21:45

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I wondered about that too - but the code seems clear enough.

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TheComet

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Posted: 4th Jun 2014 22:14 Edited at: 4th Jun 2014 22:17

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Quote: "What's a mouse positive edge? This sounds suspiciously handy if it means what I think it means."

The term "positive edge" is derived from electronics in the field of digital signal processing.

Basically, if you were to plot the value of mouseclick() over time when a user clicks, you'd get something like the following, where each vertical line represents one execution of the DBP main loop.

The positive edge is on the left side where the signal rises to become a binary "1". There is also a negative edge, which is on the right side where the signal falls to being a become "0".

In order to detect a positive edge, you require at least two sample points. I did this by saving an old state, delaying the signal by one loop:

Let c be the current mouse state (green) and o be the old mouse state (blue), a positive edge p exists when c&~o, and a negative edge n exists when ~c&o, where ~ represents an inversion of all bits and & represents a bitwise AND operation.

Plotting p and n over time results in the following:

mouseclick() encodes button presses as "1" for left-click, "2" for right-click and "4" for middle click. Those familiar with bitwise operators will already know that these are single bits which when OR-ed together slot perfectly next to each other, i.e. 1||2||4 = 7, or %001||%010||%100 = %111.

My example takes advantage of these facts, and processes the positive edge for all 3 buttons at the same time.

I neatened it up a little and posted it on the code snippets board:
http://forum.thegamecreators.com/?m=forum_view&t=211243&b=6&p=0

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Zero G Scott

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Posted: 5th Jun 2014 07:13

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This appears to make clicking and dragging a lot easier to manage, at least that's what my small mind gleams from this gem. I'm curious to know what other uses might this be helpful for? Thank you for posting this info TheComet!

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TheComet

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Posted: 5th Jun 2014 13:38 Edited at: 5th Jun 2014 13:39

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Quote: "This appears to make clicking and dragging a lot easier to manage"

That's a great example! Dragging something becomes as simple as:

+ Code Snippet

if Mouse.posEdge then pickUpItem()
If Mouse.negEdge then dropItem()

It generally makes more sense to trigger everything on positive edges. In FPS games for example, shooting is as simple as:

+ Code Snippet

if Mouse.posEdge then singleShot()  // single bullet per click
if Mouse.state then autoShoot()  // machine gun

GUI elements (buttons, checkboxes, etc.) generally are better when triggered on negative edges. Windows does this too: If you click and hold the mouse on a button, you can still drag your mouse away before releasing again.

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gamerboots

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Posted: 7th Jun 2014 14:34

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You can also use the inc and dec commands.
a=a+1
is the same as
inc a

they will never know what bit them until its too late...

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Burning Feet Man

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Posted: 17th Sep 2014 10:00

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I tie all my DBPro mouse needs in with the Windows User32.DLL, as I find DBPro bounds the mouse in a couple of limiting ways. Once you've geared your DBPro projects to use User32.DLL for mouse tracking, the world is your oyster!

Here are some of the variables that I capture;

+ Code Snippet

	Type Type_Mouse_Event
		GetAsyncKeyState As Dword 	`DLL Mouse Button State
		Getdoubleclicktime as Dword	`DLL Double Click Time
		Cursor As Type_Mouse_Value 	`Cursor Coords - (Desktop & App using sub UDT)
		Click_1 As Type_Mouse_Value	`Quick click Action, combined press/release
		Click_2 As Type_Mouse_Value	`Long click action, combined press/release
		Press_1 As Type_Mouse_Value	`Single press
		Press_2 As Type_Mouse_Value	`Double press
		Release_1 As Type_Mouse_Value	`Single Release
		Release_2 As Type_Mouse_Value	`Double Release (double click call)
		Hold_1 As Type_Mouse_Value 	`Button Held
		Hold_2 As Type_Mouse_Value 	`Button Held For more than 1 second
	Endtype

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ShellfishGames

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Posted: 21st Sep 2014 02:25

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What exactly does the ".." operator do?

Quote: "
mouse_positive_edge = (mouseclick()..7)&&mouse_last_state
"

I've tried it with a bunch of numbers, the second operand doesn't seem to have any effect, it just inverts all bits. I was aware of &&, || and ~~, but haven't seen .. yet?

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TheComet

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Posted: 21st Sep 2014 11:49

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From the documentation:

+ Code Snippet

BITWISE OPERATORS

Bitwise operators, unlike boolean operators work on all the bits of the specified variable or value. There are six bitwise operators as follows:


BITWISE LSHIFT using two less-than symbols will shift all bits one space to the left. %0111 becomes %1110.
BITWISE RSHIFT using two greater-than symbols will shift all bits one space to the right. %0111 becomes %0011.
BITWISE AND signified by the symbol && will AND all bits of one value with another. %1111 && %0011 becomes %0011.
BITWISE OR signified by the symbol || will OR all bits of one value with another. %1111 || %0011 becomes %1111.
BITWISE XOR signified by the symbol ~~ will XOR all bits of one value with another. %1111 ~~ %0011 becomes %1100.
BITWISE NOT signified by the symbol .. will NOT all bits of the right value. %1111 .. %1010 becomes %0101.

(mouseclick()..0x07) inverts the first 3 bits (bit0=left button, bit1=right button, bit2=middle button)

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Green Gandalf

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Posted: 21st Sep 2014 18:23

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I didn't understand that - nor do I see the point of that operator. What is the purpose of the second operand?

I think the Help file you quote is wrong. Try this:

+ Code Snippet

print %1111..%1111 ` second, i.e. RIGHT hand, operand has no effect - try it
print %11111111111111111111111111110000
wait key

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DarkBASIC Professional Discussion / How to change the value of a variable