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  • Is it possible to pass arithmatic operators to a method in java?

    - by user349611
    Right now I'm going to have to write a method that looks like this: public String Calculate(String Operator, Double Operand1, Double Operand2) { if (Operator.equals("+")) { return String.valueOf(Operand1 + Operand2); } else if (Operator.equals("-")) { return String.valueOf(Operand1 - Operand2); } else if (Operator.equals("*")) { return String.valueOf(Operand1 * Operand2); } else { return "error..."; } } It would be nice if I could write the code more like this: public String Calculate(String Operator, Double Operand1, Double Operand2) { return String.valueOf(Operand1 Operator Operand2); } So Operator would replace the Arithmetic Operators (+, -, *, /...) Does anyone know if something like this is possible in java?

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  • How does the ? make a quantifier lazy in regex

    - by Uriel Katz
    I've been looking into regex lately and figured that the ? operator makes the *,+, or ? lazy. My question is how does it do that? Is it that *? for example is a special operator, or does the ? have an effect on the *? In other words, does regex recognize *? as one operator in itself, or does regex recognize *? as the two separate operators * and ?? If it is the case that *? is being recognized as two separate operators, how does the ? affect the * to make it lazy. If ? means that the * is optional, shouldn't this mean that the * doesn't have to exists at all. If so, then in a statement .*? wouldn't regex just match separate letters and the whole string instead of the shorter string? Please explain, I'm desperate to understand.

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  • How to automatically display relationships in logical diagram?

    - by Cliff Chaney
    Consider a Logical Model where Entity A and Entity B are connected via Relationship Z. If I create a Logical Diagram (note: not another logical MODEL), I am able to drag Entity A and Entity B onto the diagram. Since the Logical Model already "knows" that Entity A and Entity B have a relationship, I would like to be able to easily add it to my logical diagram. I am already aware of the "Show Symbols" option whereby I can select the specific relationship that I want and have it appear. That is not a solution for me. The problem is that I have a LARGE logical model consisting of HUNDREDS of Entities and their various relationships. I then need to create application-specific diagrams consisting of a subset of those entities. I can easily identify and drag the 50+ entities onto a new diagram. But identifying and selecting all the associations is an exercise in frustration. Is there an option or some sort of feature that I'm missing - or any other trick - that would allow me to add only the relationships between selected entities or all entities on a diagram?

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  • Execute process conditionally in Windows PowerShell (e.g. the && and || operators in Bash)

    - by Dustin
    I'm wondering if anybody knows of a way to conditionally execute a program depending on the exit success/failure of the previous program. Is there any way for me to execute a program2 immediately after program1 if program1 exits successfully without testing the LASTEXITCODE variable? I tried the -band and -and operators to no avail, though I had a feeling they wouldn't work anyway, and the best substitute is a combination of a semicolon and an if statement. I mean, when it comes to building a package somewhat automatically from source on Linux, the && operator can't be beaten: # Configure a package, compile it and install it ./configure && make && sudo make install PowerShell would require me to do the following, assuming I could actually use the same build system in PowerShell: # Configure a package, compile it and install it .\configure ; if ($LASTEXITCODE -eq 0) { make ; if ($LASTEXITCODE -eq 0) { sudo make install } } Sure, I could use multiple lines, save it in a file and execute the script, but the idea is for it to be concise (save keystrokes). Perhaps it's just a difference between PowerShell and Bash (and even the built-in Windows command prompt which supports the && operator) I'll need to adjust to, but if there's a cleaner way to do it, I'd love to know.

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  • How to paste text and variables into a logical expression in R?

    - by Jasper
    I want to paste variables in the logical expression that I am using to subset data, but the subset function does not see them as column names when pasted (either with ot without quotes). I have a dataframe with columns named col1, col2 etc. I want to subset for the rows in which colx < 0.05 This DOES work: subsetdata<-subset(dataframe, col1<0.05) subsetdata<-subset(dataframe, col2<0.05) This does NOT work: for (k in 1:2){ subsetdata<-subset(dataframe, paste("col",k,sep="")<0.05) } for (k in 1:2){ subsetdata<-subset(dataframe, noquote(paste("col",k,sep=""))<0.05) } I can't find the answer; any suggestions?

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  • Cloud Computing - Multiple Physical Computers, One Logical Computer

    - by Koobz
    I know that you can set up multiple virtual machines per physical computer. I'm wondering if it's possible to make multiple physical computers behave as one logical unit? Fundamentally the way I imagine it working is that you can throw 10 computers into a facility one day. You've got one client that requires the equivalent of two computers worth, and 100 others that eat up the remaining 8. As demands change you're just reallocating logical resources, maybe the 2 computer client now requires a third physical system. You just add it to the cloud, and don't worry about sharding the database, or migrating data over to a new server. Can it work this way? If yes, why would anyone ever do things like partition their database servers anymore? Just add more computing resources. You scale horizontally with the hardware, but your server appears to scale vertically. There's no need to modify your application's infrastructure to support multiple databases etc.

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  • Cloud Computing - Multiple Physical Computers, One Logical Computer

    - by bundini
    I know that you can set up multiple virtual machines per physical computer. I'm wondering if it's possible to make multiple physical computers behave as one logical unit? Fundamentally the way I imagine it working is that you can throw 10 computers into a facility one day. You've got one client that requires the equivalent of two computers worth, and 100 others that eat up the remaining 8. As demands change you're just reallocating logical resources, maybe the 2 computer client now requires a third physical system. You just add it to the cloud, and don't worry about sharding the database, or migrating data over to a new server. Can it work this way? If yes, why would anyone ever do things like hand partition their database servers anymore? Just add more computing resources. You scale horizontally with the hardware, but your server appears to scale vertically. There's no need to modify your application's supporting infrastructure to support multiple databases etc.

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  • Changing default logical filename in SQL 2005

    - by Andrew
    I have a issue about creating databases in SQL 2005. I want to be able to change the default logical filename for the mdf file. At the moment the log logical filename ends in _log by default. I want the data logical filename to automatically end with _data for consistency. Is there a way i can set this? Andrew

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  • User reduced LVM logical volume without resizing filesystem

    - by Matthew
    I received an email yesterday that one of our users was trying to make room for a heartbeat/clustering package which requires its own partition to act as a voting disk. To do this, he attempted to reduce the size of the root partition's logical volume, and then create a new logical volume for this purpose. However, he forgot to resize the filesystem first (or include the -r switch in the command). He also forgot to unmount the root partition by running this process from a rescue cd. The system is now refusing to boot into the OS with the following error: Either the superblock or the partition table is likely to be corrupt! Unexpected Inconsistency; run fsck manually. The system them drops the user into single user mode. Is it possible to rescue the filesystem, or is it hosed? Its running ext3.

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  • "reduce" or "apply" using logical functions in Clojure

    - by Alex B
    I cannot use logical functions on a range of booleans in Clojure (1.2). Neither of the following works due to logical functions being macros: (reduce and [... sequence of bools ...]) (apply or [... sequence of bools ...]) The error saying that I "can't take value of a macro: #'clojure.core/and". How to apply these logical functions (macros) without writing boilerplate code?

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  • How to recover logical volume deleted with lvremove

    - by John P
    I am on CentOS 5.5 and am running Xen. I have a large volume group that I create logical volumes on using lvcreate. Today I had a customer cancel her account, then change her mind about an hour later. Unfortunately I had already removed the LVM her Xen image resided on. (just using a standard lvremove ). There has been no other LVM activity on this disk since then (nothing else added or deleted). Is it possible to "undo" a lvremove, or recover logical volume? If so, how would I go about it?

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  • Is there a Generic USB TouchScreen Driver 12.04?

    - by lbjoum
    Is there a Generic USB TouchScreen Driver 12.04? Device 03eb:201c I've been looking for 4 days solid (not very skilled) and can't find a solution. I have a generic tablet: C97- Atom N2600 9.7" 2GB 32GB Bluetooth WiFi WebCam Ext.3G Windows 7 Tablet PC Using 12.04 and cannot find a driver. I installed android and the touchscreen works but still lots of other bugs. Oh well, stuck with Windows 7 and not happy about it. Will keep trying, but too much time wasted already. If you have a solution I would love to try it. ubuntu@ubuntu:~$ lsusb Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 002: ID 0cf2:6238 ENE Technology, Inc. Bus 001 Device 003: ID 1a40:0101 Terminus Technology Inc. 4-Port HUB Bus 001 Device 005: ID 05e1:0100 Syntek Semiconductor Co., Ltd 802.11g + Bluetooth Wireless Adapter Bus 001 Device 006: ID 090c:3731 Silicon Motion, Inc. - Taiwan (formerly Feiya Technology Corp.) Bus 003 Device 002: ID 03eb:201c Atmel Corp. at90usbkey sample firmware (HID mouse) (from Windows: HID\VID_03EB&PID_201C\6&5F38127&0&0000 USB\VID_03EB&PID_201C\5&193ADADC&1&2 ) Bus 001 Device 007: ID 0518:0001 EzKEY Corp. USB to PS2 Adaptor v1.09 Bus 001 Device 008: ID 192f:0916 Avago Technologies, Pte. ubuntu@ubuntu:~$ sudo lsusb -v Bus 003 Device 002: ID 03eb:201c Atmel Corp. at90usbkey sample firmware (HID mouse) Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 2.00 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 32 idVendor 0x03eb Atmel Corp. idProduct 0x201c at90usbkey sample firmware (HID mouse) bcdDevice 45.a2 iManufacturer 1 CDT iProduct 2 9.75 iSerial 0 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 34 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0x00 (Missing must-be-set bit!) (Bus Powered) MaxPower 100mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 1 bInterfaceClass 3 Human Interface Device bInterfaceSubClass 0 No Subclass bInterfaceProtocol 0 None iInterface 0 HID Device Descriptor: bLength 9 bDescriptorType 33 bcdHID 1.11 bCountryCode 0 Not supported bNumDescriptors 1 bDescriptorType 34 Report wDescriptorLength 177 Report Descriptors: ** UNAVAILABLE ** Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x81 EP 1 IN bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0020 1x 32 bytes bInterval 5 Device Status: 0x00fb Self Powered Remote Wakeup Enabled Debug Mode ubuntu@ubuntu:~$ sudo lshw ubuntu description: Notebook product: To be filled by O.E.M. (To be filled by O.E.M.) vendor: To be filled by O.E.M. version: To be filled by O.E.M. serial: To be filled by O.E.M. width: 32 bits capabilities: smbios-2.7 dmi-2.7 smp-1.4 smp configuration: boot=normal chassis=notebook cpus=2 family=To be filled by O.E.M. sku=To be filled by O.E.M. uuid=00020003-0004-0005-0006-000700080009 *-core description: Motherboard product: Tiger Hill vendor: INTEL Corporation physical id: 0 version: To be filled by O.E.M. serial: To be filled by O.E.M. slot: To be filled by O.E.M. *-firmware description: BIOS vendor: American Megatrends Inc. physical id: 0 version: 4.6.5 date: 08/24/2012 size: 64KiB capacity: 960KiB capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb biosbootspecification *-cpu:0 description: CPU product: Intel(R) Atom(TM) CPU N2600 @ 1.60GHz vendor: Intel Corp. physical id: 4 bus info: cpu@0 version: 6.6.1 serial: 0003-0661-0000-0000-0000-0000 slot: CPU 1 size: 1600MHz capacity: 1600MHz width: 64 bits clock: 400MHz capabilities: x86-64 boot fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc arch_perfmon pebs bts nonstop_tsc aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm movbe lahf_lm arat configuration: cores=2 enabledcores=1 id=2 threads=2 *-cache:0 description: L1 cache physical id: 5 slot: L1-Cache size: 24KiB capacity: 24KiB capabilities: internal write-back unified *-cache:1 description: L2 cache physical id: 6 slot: L2-Cache size: 512KiB capacity: 512KiB capabilities: internal varies unified *-logicalcpu:0 description: Logical CPU physical id: 2.1 width: 64 bits capabilities: logical *-logicalcpu:1 description: Logical CPU physical id: 2.2 width: 64 bits capabilities: logical *-logicalcpu:2 description: Logical CPU physical id: 2.3 width: 64 bits capabilities: logical *-logicalcpu:3 description: Logical CPU physical id: 2.4 width: 64 bits capabilities: logical *-memory description: System Memory physical id: 28 slot: System board or motherboard size: 2GiB *-bank:0 description: SODIMM [empty] product: [Empty] vendor: [Empty] physical id: 0 serial: [Empty] slot: DIMM0 *-bank:1 description: SODIMM DDR3 Synchronous 800 MHz (1.2 ns) vendor: 69 physical id: 1 serial: 00000210 slot: DIMM1 size: 2GiB width: 64 bits clock: 800MHz (1.2ns) *-cpu:1 physical id: 1 bus info: cpu@1 version: 6.6.1 serial: 0003-0661-0000-0000-0000-0000 size: 1600MHz capabilities: ht configuration: id=2 *-logicalcpu:0 description: Logical CPU physical id: 2.1 capabilities: logical *-logicalcpu:1 description: Logical CPU physical id: 2.2 capabilities: logical *-logicalcpu:2 description: Logical CPU physical id: 2.3 capabilities: logical *-logicalcpu:3 description: Logical CPU physical id: 2.4 capabilities: logical *-pci description: Host bridge product: Atom Processor D2xxx/N2xxx DRAM Controller vendor: Intel Corporation physical id: 100 bus info: pci@0000:00:00.0 version: 03 width: 32 bits clock: 33MHz *-display UNCLAIMED description: VGA compatible controller product: Atom Processor D2xxx/N2xxx Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 09 width: 32 bits clock: 33MHz capabilities: pm msi vga_controller bus_master cap_list configuration: latency=0 resources: memory:dfe00000-dfefffff ioport:f100(size=8) *-multimedia description: Audio device product: N10/ICH 7 Family High Definition Audio Controller vendor: Intel Corporation physical id: 1b bus info: pci@0000:00:1b.0 version: 02 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: driver=snd_hda_intel latency=0 resources: irq:42 memory:dff00000-dff03fff *-pci:0 description: PCI bridge product: N10/ICH 7 Family PCI Express Port 1 vendor: Intel Corporation physical id: 1c bus info: pci@0000:00:1c.0 version: 02 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:40 ioport:2000(size=4096) memory:80000000-801fffff ioport:80200000(size=2097152) *-usb:0 description: USB controller product: N10/ICH 7 Family USB UHCI Controller #1 vendor: Intel Corporation physical id: 1d bus info: pci@0000:00:1d.0 version: 02 width: 32 bits clock: 33MHz capabilities: uhci bus_master configuration: driver=uhci_hcd latency=0 resources: irq:23 ioport:f0a0(size=32) *-usb:1 description: USB controller product: N10/ICH 7 Family USB UHCI Controller #2 vendor: Intel Corporation physical id: 1d.1 bus info: pci@0000:00:1d.1 version: 02 width: 32 bits clock: 33MHz capabilities: uhci bus_master configuration: driver=uhci_hcd latency=0 resources: irq:19 ioport:f080(size=32) *-usb:2 description: USB controller product: N10/ICH 7 Family USB UHCI Controller #3 vendor: Intel Corporation physical id: 1d.2 bus info: pci@0000:00:1d.2 version: 02 width: 32 bits clock: 33MHz capabilities: uhci bus_master configuration: driver=uhci_hcd latency=0 resources: irq:18 ioport:f060(size=32) *-usb:3 description: USB controller product: N10/ICH 7 Family USB UHCI Controller #4 vendor: Intel Corporation physical id: 1d.3 bus info: pci@0000:00:1d.3 version: 02 width: 32 bits clock: 33MHz capabilities: uhci bus_master configuration: driver=uhci_hcd latency=0 resources: irq:16 ioport:f040(size=32) *-usb:4 description: USB controller product: N10/ICH 7 Family USB2 EHCI Controller vendor: Intel Corporation physical id: 1d.7 bus info: pci@0000:00:1d.7 version: 02 width: 32 bits clock: 33MHz capabilities: pm debug ehci bus_master cap_list configuration: driver=ehci_hcd latency=0 resources: irq:23 memory:dff05000-dff053ff *-pci:1 description: PCI bridge product: 82801 Mobile PCI Bridge vendor: Intel Corporation physical id: 1e bus info: pci@0000:00:1e.0 version: e2 width: 32 bits clock: 33MHz capabilities: pci subtractive_decode bus_master cap_list *-isa description: ISA bridge product: NM10 Family LPC Controller vendor: Intel Corporation physical id: 1f bus info: pci@0000:00:1f.0 version: 02 width: 32 bits clock: 33MHz capabilities: isa bus_master cap_list configuration: latency=0 *-storage description: SATA controller product: N10/ICH7 Family SATA Controller [AHCI mode] vendor: Intel Corporation physical id: 1f.2 bus info: pci@0000:00:1f.2 logical name: scsi0 version: 02 width: 32 bits clock: 66MHz capabilities: storage msi pm ahci_1.0 bus_master cap_list emulated configuration: driver=ahci latency=0 resources: irq:41 ioport:f0f0(size=8) ioport:f0e0(size=4) ioport:f0d0(size=8) ioport:f0c0(size=4) ioport:f020(size=16) memory:dff04000-dff043ff *-disk description: ATA Disk product: BIWIN SSD physical id: 0.0.0 bus info: scsi@0:0.0.0 logical name: /dev/sda version: 1206 serial: 123403501060 size: 29GiB (32GB) capabilities: partitioned partitioned:dos configuration: ansiversion=5 signature=8fbe402b *-volume:0 description: Windows NTFS volume physical id: 1 bus info: scsi@0:0.0.0,1 logical name: /dev/sda1 version: 3.1 serial: 249bde5d-8246-9a40-88c7-2d5e3bcaf692 size: 19GiB capacity: 19GiB capabilities: primary bootable ntfs initialized configuration: clustersize=4096 created=2011-04-04 02:27:51 filesystem=ntfs state=clean *-volume:1 description: Windows NTFS volume physical id: 2 bus info: scsi@0:0.0.0,2 logical name: /dev/sda2 version: 3.1 serial: de12d40f-d5ca-8642-b306-acd9349fda1a size: 10231MiB capacity: 10GiB capabilities: primary ntfs initialized configuration: clustersize=4096 created=2011-04-04 01:52:26 filesystem=ntfs state=clean *-serial UNCLAIMED description: SMBus product: N10/ICH 7 Family SMBus Controller vendor: Intel Corporation physical id: 1f.3 bus info: pci@0000:00:1f.3 version: 02 width: 32 bits clock: 33MHz configuration: latency=0 resources: ioport:f000(size=32) *-scsi:0 physical id: 2 bus info: usb@1:1 logical name: scsi4 capabilities: emulated scsi-host configuration: driver=usb-storage *-disk description: SCSI Disk physical id: 0.0.0 bus info: scsi@4:0.0.0 logical name: /dev/sdb size: 29GiB (31GB) capabilities: partitioned partitioned:dos configuration: signature=00017463 *-volume description: Windows FAT volume vendor: mkdosfs physical id: 1 bus info: scsi@4:0.0.0,1 logical name: /dev/sdb1 logical name: /cdrom version: FAT32 serial: 129b-4f87 size: 29GiB capacity: 29GiB capabilities: primary bootable fat initialized configuration: FATs=2 filesystem=fat mount.fstype=vfat mount.options=rw,relatime,fmask=0022,dmask=0022,codepage=cp437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro state=mounted *-scsi:1 physical id: 3 bus info: usb@1:3.1 logical name: scsi6 capabilities: emulated scsi-host configuration: driver=usb-storage *-disk description: SCSI Disk physical id: 0.0.0 bus info: scsi@6:0.0.0 logical name: /dev/sdc size: 7400MiB (7759MB) capabilities: partitioned partitioned:dos configuration: signature=c3072e18 *-volume description: Windows FAT volume vendor: mkdosfs physical id: 1 bus info: scsi@6:0.0.0,1 logical name: /dev/sdc1 logical name: /media/JOUM8G version: FAT32 serial: e676-9311 size: 7394MiB capacity: 7394MiB capabilities: primary bootable fat initialized configuration: FATs=2 filesystem=fat label=Android mount.fstype=vfat mount.options=rw,nosuid,nodev,relatime,uid=999,gid=999,fmask=0022,dmask=0077,codepage=cp437,iocharset=iso8859-1,shortname=mixed,showexec,utf8,flush,errors=remount-ro state=mounted ubuntu@ubuntu:~$ ubuntu@ubuntu:~$ xinput list ? Virtual core pointer id=2 [master pointer (3)] ? ? Virtual core XTEST pointer id=4 [slave pointer (2)] ? ? Plus More Enterprise LTD. USB-compliant keyboard id=10 [slave pointer (2)] ? ? USB Optical Mouse id=11 [slave pointer (2)] ? Virtual core keyboard id=3 [master keyboard (2)] ? Virtual core XTEST keyboard id=5 [slave keyboard (3)] ? Power Button id=6 [slave keyboard (3)] ? Power Button id=7 [slave keyboard (3)] ? Sleep Button id=8 [slave keyboard (3)] ? Plus More Enterprise LTD. USB-compliant keyboard id=9 [slave keyboard (3)] ? USB 2.0 Webcam - Front id=12 [slave keyboard (3)] ? AT Translated Set 2 keyboard id=13 [slave keyboard (3)] ubuntu@ubuntu:~$

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  • Is it possible to implement bitwise operators using integer arithmetic?

    - by Statement
    Hello World! I am facing a rather peculiar problem. I am working on a compiler for an architecture that doesn't support bitwise operations. However, it handles signed 16 bit integer arithmetics and I was wondering if it would be possible to implement bitwise operations using only: Addition (c = a + b) Subtraction (c = a - b) Division (c = a / b) Multiplication (c = a * b) Modulus (c = a % b) Minimum (c = min(a, b)) Maximum (c = max(a, b)) Comparisons (c = (a < b), c = (a == b), c = (a <= b), et.c.) Jumps (goto, for, et.c.) The bitwise operations I want to be able to support are: Or (c = a | b) And (c = a & b) Xor (c = a ^ b) Left Shift (c = a << b) Right Shift (c = a b) (All integers are signed so this is a problem) Signed Shift (c = a b) One's Complement (a = ~b) (Already found a solution, see below) Normally the problem is the other way around; how to achieve arithmetic optimizations using bitwise hacks. However not in this case. Writable memory is very scarce on this architecture, hence the need for bitwise operations. The bitwise functions themselves should not use a lot of temporary variables. However, constant read-only data & instruction memory is abundant. A side note here also is that jumps and branches are not expensive and all data is readily cached. Jumps cost half the cycles as arithmetic (including load/store) instructions do. On other words, all of the above supported functions cost twice the cycles of a single jump. Some thoughts that might help: I figured out that you can do one's complement (negate bits) with the following code: // Bitwise one's complement b = ~a; // Arithmetic one's complement b = -1 - a; I also remember the old shift hack when dividing with a power of two so the bitwise shift can be expressed as: // Bitwise left shift b = a << 4; // Arithmetic left shift b = a * 16; // 2^4 = 16 // Signed right shift b = a >>> 4; // Arithmetic right shift b = a / 16; For the rest of the bitwise operations I am slightly clueless. I wish the architects of this architecture would have supplied bit-operations. I would also like to know if there is a fast/easy way of computing the power of two (for shift operations) without using a memory data table. A naive solution would be to jump into a field of multiplications: b = 1; switch (a) { case 15: b = b * 2; case 14: b = b * 2; // ... exploting fallthrough (instruction memory is magnitudes larger) case 2: b = b * 2; case 1: b = b * 2; } Or a Set & Jump approach: switch (a) { case 15: b = 32768; break; case 14: b = 16384; break; // ... exploiting the fact that a jump is faster than one additional mul // at the cost of doubling the instruction memory footprint. case 2: b = 4; break; case 1: b = 2; break; }

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  • Two '==' equality operators in same 'if' condition are not working as intended.

    - by Manav MN
    I am trying to establish equality of three equal variables, but the following code is not printing the obvious true answer which it should print. Can someone explain, how the compiler is parsing the given if condition internally? #include<stdio.h> int main() { int i = 123, j = 123, k = 123; if ( i == j == k) printf("Equal\n"); else printf("NOT Equal\n"); return 0; } Output: manav@workstation:~$ gcc -Wall -pedantic calc.c calc.c: In function ‘main’: calc.c:5: warning: suggest parentheses around comparison in operand of ‘==’ manav@workstation:~$ ./a.out NOT Equal manav@workstation:~$ EDIT: Going by the answers given below, is the following statement okay to check above equality? if ( (i==j) == (j==k))

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  • Postfix and right-associative operators in LR(0) parsers

    - by Ian
    Is it possible to construct an LR(0) parser that could parse a language with both prefix and postfix operators? For example, if I had a grammar with the + (addition) and ! (factorial) operators with the usual precedence then 1+3! should be 1 + 3! = 1 + 6 = 7, but surely if the parser were LR(0) then when it had 1+3 on the stack it would reduce rather than shift? Also, do right associative operators pose a problem? For example, 2^3^4 should be 2^(3^4) but again, when the parser have 2^3 on the stack how would it know to reduce or shift? If this isn't possible is there still a way to use an LR(0) parser, possibly by converting the input into Polish or Reverse Polish notation or adding brackets in the appropriate places? Would this be done before, during or after the lexing stage?

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  • What is the difference between the * and the & operators in c programming?

    - by Wesley
    I am just making sure I understand this concept correctly. With the * operator, I make a new variable, which is allocated a place in memory. So as to not unnecessarily duplicate variables and their values, the & operator is used in passing values to methods and such and it actually points to the original instance of the variable, as opposed to making new copies...Is that right? It is obviously a shallow understanding, but I just want to make sure I am not getting them mixed up. Thanks!

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  • C/C++: Who uses the logical operator macros from iso646.h and why?

    - by Jaime Soto
    There has been some debate at work about using the merits of using the alternative spellings for C/C++ logical operators in iso646.h: and && and_eq &= bitand & bitor | compl ~ not ! not_eq != or || or_eq |= xor ^ xor_eq ^= According to Wikipedia, these macros facilitate typing logical operators in international (non-US English?) and non-QWERTY keyboards. All of our development team is in the same office in Orlando, FL, USA and from what I have seen we all use the US English QWERTY keyboard layout; even Dvorak provides all the necessary characters. Supporters of using the iso646.h macros claim we should them because they are part of the C and C++ standards. I think this argument is moot since digraphs and trigraphs are also part of these standards and they are not even supported by default in many compilers. My rationale for opposing these macros in our team is that we do not need them since: Everybody on our team uses the US English QWERTY keyboard layout; C and C++ programming books from the US barely mention iso646.h, if at all; and new developers may not be familiar with iso646.h (this is expected if they are from the US). /rant Finally, to my set of questions: Does anyone in this site use the iso646.h logical operator macros? Why? What is your opinion about using the iso646.h logical operator macros in code written and maintained on US English QWERTY keyboards? Is my digraph and trigraph analogy a valid argument against using iso646.h with US English QWERTY keyboard layouts? EDIT: I missed two similar questions in StackOverflow: Is anybody using the named boolean operators? Which C++ logical operators do you use: and, or, not and the ilk or C style operators? why?

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  • Why would one overload the && and & operator?

    - by acidzombie24
    The same question goes for | and ||. Why would one overload or 'use' the & and && operator? The only use i thought of are Bitwise Ands for int base types (but not float/decimals) using & logical short circuit for bools/functions that return bool. Using the && operator usually. I cant think of any classes that use those operators. Absolutely none. I know a class might support + (and not '-') which combine two strings together. I seen an object such as datetime overload '-' so two dates can be subtracted to make a timespan (obviously you cant add two dates) but i never seen &, &&, | and || used. Does anyone know of a use? In any language?

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  • Combining two operators in Evil-mode Emacs

    - by Dyslexic Tangent
    In vim I've remapped > and < when in visual mode to >gv and <gv respectively, like so: vnoremap > >gv vnoremap < <gv Since my target for this question are folks experienced with emacs and not vim, what > and < do is indent/dedent visually selected text. What gv does is reselect the previously selected text. These maps cause > and < to indent/dedent and then reselect the previously selected text. I'm trying out emacs with evil-mode and I'd like to do the same, but I'm having some difficulty figuring out how, exactly, to accomplish the automatic reselection. It looks like I need to somehow call evil-shift-right and evil-visual-restore sequentially, but I don't know how to create a map that will do both, so I tried creating my own function which would call both sequentially and map that instead, but it didn't work, possibly due to the fact that both of them are defined, not as functions with defun but instead as operators with evil-define-operator. I tried creating my own operators: (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) (evil-visual-restore)) (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) (evil-visual-restore)) but that doesn't restore visual as expected. A stab in the dark gave me this: (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) ('evil-visual-restore)) (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) ('evil-visual-restore)) but that selects one additional line whenever it is supposed to reselect. For now I've been using the following, which only has the problem where it reselects an additional line in the < operator. (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) (evil-visual-make-selection beg end)) (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) (evil-visual-make-selection beg end)) and I've mapped them: (define-key evil-visual-state-map ">" 'shift-right-reselect) (define-key evil-visual-state-map "<" 'shift-left-reselect) any help / pointers / tips would be greatly appreciated. Thanks in advance.

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  • Nagios3: Conditional operators for service checks?

    - by Dave
    I'm trying to setup Nagios to monitor my various using hostgroups to define 'machine roles', against which I run services to check the machines by role. However, I'd like to use conditional operators that would enable me to run the service check against an intersection of two host groups, rather than their unions... i.e. using &&, ||, or () operators. For example, imagine I have the following servers: www-eu: Linux WWW (Apache) server, in the EU www-us: Windows WWW (IIS) server, in the US (West coast) ftp-eu: Linux FTP server, in the EU ftp-us: Windows FTP server, in the US I would want to create the following host groups: US-Servers: www-us, ftp-us EU-Servers: www-eu, ftp-eu WWW-Servers: www-us, www-eu FTP-Servers: ftp-us, ftp-eu Now say I'm interested in checking the HTTP response time for my web servers. Then let's say this particular Nagios service is running from the US (West Coast), and that I have a command called *check_http_response_time*. This command will check the responsiveness of the HTTP server, which I can provide an argument which defines the max response time before raising critical. My command might look like: check_http_response_time $HOSTNAME$ 50 Now traditionally, I can run my checks by specifying a list of host or hostgroups. define service{ use local-service hostgroup_name WWW-Servers # Servers = www-us, www-eu servicegroups WWW Checks service_description Check HTTP Response Time check_command check_http_response_time!50 } However, with the above service definition, given my Nagios service is in US West, I could reasonably expect that my EU server will return critical. Really, I want different thresholds for each region (50 for US West, 200 for EU.) I would have to permutate my service for each host and set their custom threshold, or alternatively permutate out my service groups by role & region (i.e. WWW-Servers-EU), and run my specific thresholds against those. Though the latter is better, both are much messier than I'd like... What I would love, and what this post is asking for, is a way to use hostgroups to perform an intersection using conditional logic, rather than a simple union. It might look like: define service{ use local-service hostgroup_name WWW-Servers && US-Servers servicegroups WWW Checks service_description Check HTTP Response Time check_command check_http_response_time!50 } It then would run the check only against servers that are in both WWW-Servers and US-Servers, in my example, just www-us. The benefits of such a feature would be significant for Nagios services configured for large-scale. Is this feature available? If it isn't, will it be available in the future? Is there an alternative way to accomplish this given the most recent Nagios version? Any tips/suggestions are most appreciated! Dave

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