In Visual Basic
Friend Const xxx As UInt64 = 400 * 365 * 24 * 60 * 60 ''// Number of secs in 400 years
This fails with the error
constant expression not representable in type integer
The problem is 400 * 365 * 24 * 60 * 60 is larger than 2^32
I would have thought that by declaring the constant to be UInt64 that it would be OK to assign a 64 bit value to it
Aside from the fact that there are slightly more than 365 days each year (you need to add 97 leap days), each of the values that are multiplied to make up your constant are integer literals, and therefore until you assign them to the UInt64 it's all done in integer space. Try this:
Friend Const xxx As UInt64 = 400UL * 365UL * 24UL * 60UL * 60UL
Put a hash at the end of the constant, and declare it as a 'double'...
I did this with my bitmask fields:
Public Const EDIT_TRANSACTION As Double = 1073741824
Public Const EDIT_DWRDELIVERY As Double = 2147483648#
Public Const ENTER_DWRORDER As Double = 4294967296#
Public Const DELETE_DWRORDER As Double = 8589934592#
Public Const DELETE_TRANSACTION As Double = 17179869184#
Public Const DELETE_WATERORDER As Double = 34359738368#
Public Const ENTER_METERREADING As Double = 68719476736#
** EDIT **
I guess I got marked down on this because this was old code I wrote for VB6, and not exactly what you were asking for. So, if anyone reading this is using VB6, and have to pass Bitmask fields to something like SQL, this is what worked perfectly for me.
Otherwise, just keep voting my answer down. :)
Related
I have this code:
function somePureFunction() public pure returns(uint256){
uint8 temp = 255;
return 2 + temp;
}
This code gives:
call to SimpleStorage.somePureFunction errored: VM error: revert.
revert
The transaction has been reverted to the initial state.
Note: The called function should be payable if you send value and the value you send should be less than your current balance.
But this works:
function somePureFunction() public pure returns(uint256){
return 2 + 255;
}
In particular your problem refers to value about temp that you give to this variable.
When you declare a variable with datatype uint8 you must to put inside it a value from 0 - 255 (255 excluded). For calculate the range of a specific uint, you can use this statement:
MaximumRange = 2*[numberOfBit]-1
Example:
Issue: I want know what is the range about uint32.
Expression = 2*32-1
Result = 0 - 4294967295
In your specific case, if you change this line:
uint8 temp = 255;
with this:
uint16 temp = 255;
it'll work successfully.
NOTE: You can change current datatype temp variable with other uint datatype like: uint16, uint32, uint64 and others. You must to keep in your mind the range of a single datatype and the value that you want to store inside the variable.
Usual URL shortening techniques use few characters of the usual URL-charset, because not need more. Typical short URL is http://domain/code, where code is a integer number. Suppose that I can use any base (base10, base16, base36, base62, etc.) to represent the number.
QR Code have many encoding modes, and we can optimize the QR Code (minimal version to obtain lowest density), so we can test pairs of baseX-modeY...
What is the best base-mode pair?
NOTES
A guess...
Two modes fit with the "URL shortening profile",
0010 - Alphanumeric encoding (11 bits per 2 characters)
0100- Byte encoding (8 bits per character)
My choice was "upper case base36" and Alphanumeric (that also encodes "/", ":", etc.), but not see any demonstration that it is always (for any URL-length) the best. There are some good Guide or Mathematical demonstration about this kind of optimization?
The ideal (perhaps impracticable)
There are another variation, "encoding modes can be mixed as needed within a QR symbol" (Wikipedia)... So, we can use also
HTTP://DOMAIN/ with Alphanumeric + change_mode + Numeric encoding (10 bits per 3 digits)
For long URLs (long integers), of course, this is the best solution (!), because use all charset, no loose... Is it?
The problem is that this kind of optimization (mixed mode) is not accessible in usual QRCode-image generators... it is practicable? There are one generator using correctally?
An alternative answer format
The (practicable) question is about best combination of base and mode, so we can express it as a (eg. Javascript) function,
function bestBaseMode(domain,number_range) {
var dom_len = domain.length;
var urlBase_len = dom_len+8; // 8 = "http://".length + "/".length;
var num_min = number_range[0];
var num_max = number_range[1];
// ... check optimal base and mode
return [base,mode];
}
Example-1: the domain is "bit.ly" and the code is a ISO3166-1-numeric country-code,
ranging from 4 to 894. So urlBase_len=14, num_min=4 and num_max=894.
Example-2: the domain is "postcode-resolver.org" and number_range parameter is the range of most frequent postal codes integer representations, for instance a statistically inferred range from ~999 to ~999999. So urlBase_len=27, num_min=999 and num_max=9999999.
Example-3: the domain is "my-example3.net" and number_range a double SHA-1 code, so a fixed length code with 40 bytes (2 concatenated hexadecimal 40 digits long numbers). So num_max=num_min=Math.pow(8,40).
Nobody want my bounty... I lost it, and now also need to do the work by myself ;-)
about the ideal
The goQR.me support reply the particular question about mixed encoding remembering that, unfortunately, it can't be used,
sorry, our api does not support mixed qr code encoding.
Even the standard may defined it. Real world QR code scanner apps
on mobile phone have tons of bugs, we would not recommend to rely
on this feature.
functional answer
This function show the answers in the console... It is a simplification and "brute force" solution.
/**
* Find the best base-mode pair for a short URL template as QR-Code.
* #param Msg for debug or report.
* #param domain the string of the internet domain
* #param digits10 the max. number of digits in a decimal representation
* #return array of objects with equivalent valid answers.
*/
function bestBaseMode(msg, domain,digits10) {
var commomBases= [2,8,10,16,36,60,62,64,124,248]; // your config
var dom_len = domain.length;
var urlBase_len = dom_len+8; // 8 = "http://".length + "/".length
var numb = parseFloat( "9".repeat(digits10) );
var scores = [];
var best = 99999;
for(i in commomBases) {
var b = commomBases[i];
// formula at http://math.stackexchange.com/a/335063
var digits = Math.floor(Math.log(numb) / Math.log(b)) + 1;
var mode = 'alpha';
var len = dom_len + digits;
var lost = 0;
if (b>36) {
mode = 'byte';
lost = parseInt( urlBase_len*0.25); // only 6 of 8 bits used at URL
}
var score = len+lost; // penalty
scores.push({BASE:b,MODE:mode,digits:digits,score:score});
if (score<best) best = score;
}
var r = [];
for(i in scores) {
if (scores[i].score==best) r.push(scores[i]);
}
return r;
}
Running the question examples:
var x = bestBaseMode("Example-1", "bit.ly",3);
console.log(JSON.stringify(x)) // "BASE":36,"MODE":"alpha","digits":2,"score":8
var x = bestBaseMode("Example-2", "postcode-resolver.org",7);
console.log(JSON.stringify(x)) // "BASE":36,"MODE":"alpha","digits":5,"score":26
var x = bestBaseMode("Example-3", "my-example3.net",97);
console.log(JSON.stringify(x)) // "BASE":248,"MODE":"byte","digits":41,"score":61
How would i generate a random double between 1 and a defined max in c++/cli, ive use random_number_distribution and mersenne twister in the random header before but never in cli, will this work in cli with random or system::random, or are there any similar alternatives? Thanks.
Here's how
double randDouble(double fMin, double fMax)
{
double f = (double)rand() / RAND_MAX;
return fMin + f * (fMax - fMin);
}
The System::Random class, with its NextDouble method is what you want. NextDouble will return a double >= 0.0 and < 1.0. So, to return a value between 1 and a max:
double RandOneToMax(double max)
{
Random^ r = ...;
return (r->NextDouble() * (max - 1)) + 1;
}
I'm using a for-loop to determine whether the long double is an int. I have it set up that the for loop loops another long double that is between 2 and final^1/2. Final is a loop I have set up that is basically 2 to the power of 2-10 minus 1. I am then checking if final is an integer. My question is how can I get only the final values that are integers?
My explanation may have been a bit confusing so here is my entire loop code. BTW I am using long doubles because I plan on increasing these numbers very largely.
for (long double ld = 1; ld<10; ld++) {
long double final = powl(2, ld) - 1;
//Would return e.g. 1, 3, 7, 15, 31, 63...etc.
for (long double pD = 2; pD <= powl(final, 0.5); pD++) {
//Create new long double
long double newFinal = final / pD;
//Check if new long double is int
long int intPart = (long int)newFinal;
long double newLong = newFinal - intPart;
if (newLong == 0) {
NSLog(#"Integer");
//Return only the final ints?
}
}
}
Just cast it to an int and subtract it from itself?
long double d;
//assign a value to d
int i = (int)d;
if((double)(d - i) == 0) {
//d has no fractional part
}
As a note... because of the way floating point math works in programming, this == check isn't necessarily the best thing to do. Better would be to decide on a certain level of tolerance, and check whether d was within that tolerance.
For example:
if(fabs((double)(d - i)) < 0.000001) {
//d's fractional part is close enough to 0 for your purposes
}
You can also use long long int and long double to accomplish the same thing. Just be sure you're using the right absolute value function for whatever type you're using:
fabsf(float)
fabs(double)
fabsl(long double)
EDIT... Based on clarification of the actual problem... it seems you're just trying to figure out how to return a collection from a method.
-(NSMutableArray*)yourMethodName {
NSMutableArray *retnArr = [NSMutableArray array];
for(/*some loop logic*/) {
// logic to determine if the number is an int
if(/*number is an int*/) {
[retnArr addObject:[NSNumber numberWithInt:/*current number*/]];
}
}
return retnArr;
}
Stick your logic into this method. Once you've found a number you want to return, stick it into the array using the [retnArr addObject:[NSNumber numberWithInt:]]; method I put up there.
Once you've returned the array, access the numbers like this:
[[arrReturnedFromMethod objectAtIndex:someIndex] intValue];
Optionally, you might want to throw them into the NSNumber object as different types.
You can also use:
[NSNumber numberWithDouble:]
[NSNumber numberWithLongLong:]
And there are matching getters (doubleValue,longLongValue) to extract the number. There are lots of other methods for NSNumber, but these seem the most likely you'd want to be using.
The overview tab of a process on jconsole shows me the CPU Usage percentage. Is there a MBean that gives me this value? What is its ObjectName?
Update: In Java 7 you can do it like so:
public static double getProcessCpuLoad() throws MalformedObjectNameException, ReflectionException, InstanceNotFoundException {
MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
ObjectName name = ObjectName.getInstance("java.lang:type=OperatingSystem");
AttributeList list = mbs.getAttributes(name, new String[]{ "ProcessCpuLoad" });
if (list.isEmpty()) return Double.NaN;
Attribute att = (Attribute)list.get(0);
Double value = (Double)att.getValue();
if (value == -1.0) return Double.NaN;
return ((int)(value * 1000) / 10.0); // returns a percentage value with 1 decimal point precision
}
----- original answer below -----
In Java 7 you can use the hidden methods of com.sun.management.OperatingSystemMXBean:
getProcessCpuLoad() // returns the CPU usage of the JVM
getSystemCpuLoad() // returns the CPU usage of the whole system
Both values are returned as a double between 0.0 and 1.0 so simply multiply by 100 to get a percentage.
com.sun.management.OperatingSystemMXBean osBean = ManagementFactory.getPlatformMXBean(OperatingSystemMXBean.class);
System.out.println(osBean.getProcessCpuLoad() * 100);
System.out.println(osBean.getSystemCpuLoad() * 100);
Since these are hidden, undocumented, methods that exist in com.sun.management.OperatingSystemMXBean package and not in the java.lang.management.OperatingSystemMXBean there is a risk that they will not be available in some JVMs or in future updates, so you should decide if you're willing to take that risk or not.
see https://www.java.net/community-item/hidden-java-7-features-%E2%80%93-system-and-process-cpu-load-monitoring for more.
There does not seem to be a direct MBean within ManagementFactory. The closest is http://java.sun.com/javase/6/docs/api/java/lang/management/OperatingSystemMXBean.html#getSystemLoadAverage() which can be used to calculate the CPU used by the whole system.
However this URL has suggested a method based on the source code of jconsole
I modified a code from internet, like this, then I tested that and the result almost match the linux ps command's result.
/** below is the code */
public float getCpuUsed() {
/** get a MXBean */
com.sun.management.OperatingSystemMXBean osMXBean =
(com.sun.management.OperatingSystemMXBean)
ManagementFactory.getOperatingSystemMXBean();
/** set old timestamp values */
long previousJvmProcessCpuTime = osMXBean.getProcessCpuTime();
int sleepTime = 350;
/** sleep for a while to use to calculate */
try {
TimeUnit.MILLISECONDS.sleep(sleepTime);
} catch (InterruptedException e) {
logger.error("InterruptedException occurred while MemoryCollector sleeping...");
}
/** elapsed process time is in nanoseconds */
long elapsedProcessCpuTime = osMXBean.getProcessCpuTime() - previousJvmProcessCpuTime;
/** elapsed uptime is in milliseconds */
long elapsedJvmUptime = sleepTime ;
/** total jvm uptime on all the available processors */
//long totalElapsedJvmUptime = elapsedJvmUptime * osMXBean.getAvailableProcessors() ;
long totalElapsedJvmUptime = elapsedJvmUptime;
//System.out.println("echo cpu processors num " + osMXBean.getAvailableProcessors());
/** calculate cpu usage as a percentage value
to convert nanoseconds to milliseconds divide it by 1000000 and to get a percentage multiply it by 100 */
float cpuUsage = elapsedProcessCpuTime / (totalElapsedJvmUptime * 10000F);
return (float)(Math.round(cpuUsage*10)/10);
}
Iff you are using UNIX based OS then it's way much easier
final OperatingSystemMXBean mxBean = ManagementFactory.getOperatingSystemMXBean();
if (mxBean instanceof UnixOperatingSystemMXBean) {
return ((UnixOperatingSystemMXBean) mxBean).getSystemCpuLoad() * 100.0;
}