In Python you can use print:
print("foobar")whereas in Octave you can use disp:
disp("foobar")You can print numbers using print in Python:
x = 1 print(x)
and also using disp in Octave:
x = 1 disp(x)
Note that you can use multiple argument to print in Python:
x = 1
print("The value of x is", x)whereas in Octave you need to use disp together with cstrcat:
disp(cstrcat("The value of x is ", num2str(x)))
Open a command prompt (no admin command prompt required) and run this command:
fsutil behavior query disablelastaccess
For me, this prints
DisableLastAccess = 3 (Systemverwaltet, aktiviert)
indicating that access timestamps are activated.
OCCUtils provides convenience functions for computing the orthogonal direction to two directions:
#include <occutils/Axis.hxx> using namespace OCCUtils; gp_Ax1 axis = /* ... */; gp_Pnt pnt = /* ... */; double distance = Axis::Distance(axis, pnt);
Alternatively, you can also use Point::Distance() which internally just calls Axis::Distance() but might make your code more readable under some circumstances. Note that the argument order is inverted!
#include <occutils/Point.hxx> using namespace OCCUtils; gp_Ax1 axis = /* ... */; gp_Pnt pnt = /* ... */; double distance = Point::Distance(pnt, axis);
In case you can’t use OCCUtils, here’s the code to do it manually:
double distance = gp_Lin(axis).Distance(pnt);
OCCUtils provides convenience functions for computing the orthogonal direction to two directions:
#include <occutils/Axis.hxx> using namespace OCCUtils; gp_Ax1 axis = /* ... */; gp_Png point = /* ... */; bool pointIsOnAxis = Axis::Contains(axis, point);
In case you can’t use OCCUtils, here’s the code to do it manually:
gp_Lin(axis).Contains(pnt, Precision::Confusion());
OCCUtils provides convenience functions for computing the orthogonal direction to two directions:
#include <occutils/Direction.hxx> using namespace OCCUtils; gp_Dir dir1 = /* ... */; gp_Dir dir2 = /* ... */; gp_Dir orthogonalDirection = Direction::Orthogonal(dir1, dir2);
In case you can’t use OCCUtils, here’s the code to do it manually:
gp_Dir orthogonalDirection = dir1.Crossed(dir2);
The function used is called Crossed() since the mathematical operation being used is the cross product between the two direction vectors.
OCCUtils provides convenience functions for getting the midpoint (also called the center) between 2 or more points:
#include <occutils/Point.hxx>
using namespace OCCUtils;
gp_Pnt p1 = /* ... */;
gp_Pnt p2 = /* ... */;
gp_Pnt midpointOfP1AndP2 = Point::Midpoint({p1, p2});You can also call Point::Midpoint() with a std::vector<gp_Pnt>.
In case you can’t use OCCUtils, here’s the code to do it manually:
double x = 0.0, y = 0.0, z = 0.0;
for (const gp_Pnt &pnt : points) {
x += pnt.X();
y += pnt.Y();
z += pnt.Z();
}
size_t size = points.size();
gp_Pnt midpoint(x / size, y / size, z / size);
OCCUtils provides a convenience function to do this:
#include <occutils/Shape.hxx> using namespace OCCUtils; TopoDS_Shape myShape = /* ... */; double volume = Shape::Volume(myShape);
In case you need to do this without OCCUtils, use
GProp_GProps gprops; BRepGProp::VolumeProperties(shape, gprops); double volume = gprops.Mass();
Run this command in your shell:
docker rm $(docker ps -a -q)
To stop & delete all running containers in docker use
docker rm $(docker ps -a -q) --force
Run this:
lxc launch ubuntu:22.04 mycontainer
In case you see this error message
Error: Failed container creation: No storage pool found. Please create a new storage pool
see How to fix lxd ‘Failed container creation: No storage pool found. Please create a new storage pool.’
Now you can connect to your container using
lxc exec mycontainer /bin/bash
Note: Based on this post I have published buildock on GitHub.
Many C/C++ programmers and project managers know the pain of creating a reproducible build environment for all developers: Works for me is a common meme not without a reason.
My approach is to dockerize not neccessarily the application itself but the build system, encapsulating both the specific compiler version and the system around it plus all required system-level libraries in a Docker image.
Take the obligatory Hello World in C++:
// main.cpp
#include <iostream>
using namespace std;
int main() {
cout << "Hello, World!" << endl;
return 0;
}and the corresponding Makefile:
all:
g++ -o helloworld main.cppHow can we compile this simple project without installing a compiler and GNU make on the local computer (no cheating by using build servers allowed)?
Actually it’s rather simple:
docker run --user $(id -u):$(id -g) -v $PWD:/app -it ulikoehler/ubuntu-gcc-make make
Breaking it down:
docker run: Create a new docker container and run a command in it--user $(id -u):$(id -g): This makes the docker container run with the current user’s ID and the current user’s group – both for preventing the compiler to create output files as root and to safeguard against some IT security risks. Also see How to run docker container as current user & group-v $PWD:/app: Mount the current directory ($PWD) on /app in the container. Since the Dockerfile used to build the container contains the WORKDIR /app directive, whatever command we run in the container will by default be executed in the /app directory – and therefore in the current local directory on the host.-it runs the container in interactive mode, i.e. keypressed are passed down to the command you are running. Also, this means that our command will only finish when the container has finished executing.ulikoehler/ubuntu-gcc-make: This is the image we’re using for that example. It’s nothing more than an ubuntu:18.04 base image with build-essentials and make installed and WORKDIR set to /appmake: This is the command we’ll run in the container. You can use any command here, even no command is possible (in which case the container’s default command will be used – in case of ulikoehler/ubuntu-gcc-make that is CMD [ "/usr/bin/make" ])Here’s the complete Dockerfile used to generate ulikoehler/ubuntu-gcc-make:
FROM ubuntu:18.04 RUN apt update && apt -y install build-essential make && rm -rf /var/lib/apt/lists/* WORKDIR /app CMD [ "/usr/bin/make" ]
Usually you build a docker image like
docker build -t myimagename .
but using this method you can only have one Dockerfile in each directory.
In case you don’t want to have separate directories for your Dockerfiles you can use the -f argument to docker build:
docker build -f FirstDockerfile .
Note that you still need to add . at the end so docker build knows where to COPY files from if you have COPY or similar statements in your Dockerfile.
If you want to prevent your docker container creating files as root, use
--user $(id -u):$(id -g)
as an argument to docker run. Example:
docker run --user $(id -u):$(id -g) -it -v $(pwd):/app myimage
Run
id -g
to get the GID of the current user’s primary group. Example:
$ id -g 1000
You can also get the GID of another user’s primary group:
$ id -g root 0
Run
id -u
to get the current user’s UID. Example:
$ id -u 1000
You can also get another user’s UID:
$ id -u root 0
OCCUtils provides a convenient utility to compute the Normal of a surface (represented by a GeomAdaptor_Surface) in OpenCASCADE:
#include <occutils/Surface.hxx> using namespace OCCUtils; GeomAdaptor_Surface surf = /* ... */; gp_Ax1 surfaceNormal = Surface::Normal(surf); // ...or just get the direction gp_Dir surfaceDirection = Surface::NormalDirection(surf);
This function computes the normal vector at specific U/V coordinates which default to (0,0). You can also give custom U/V coordinates:
gp_Ax1 normal = Surface::Normal(surf, 1.0 /* u */, -4.5 /* v */);
In case you can’t use OCCUtils and you need to do it manually, here’s how you can do it:
#include <GeomLProp_SLProps.hxx> GeomLProp_SLProps props(surf.Surface(), u, v, 1 /* max 1 derivation */, precision); gp_Ax1 axis(props.Value(), props.Normal());
props.Value() returns the point on the surface at the given U/V coordinates.
You are trying to run mongorestore my-backup, but you see large numbers of warning messages like this one:
- E11000 duplicate key error collection: mydb.mycollection index: _id_ dup key: { : "MyKey" }
By default, mongorestore does not overwrite or delete any existing documents. You need to tell it to drop each collection immediately before importing it from the backup:
mongorestore --drop my-backup
Any documents not in the backup will be permanently lost after running this!
Note that this will not drop collections that are not present in the backup.
mongodump --db mydb --out mydb.mongobackup
This will backup the database mydb from the MongoDB running at localhost and store the backup in the newly created DigiKey.mongobackup directory as BSON.
mongorestore mydb.mongobackup
This will restore the backup to localhost (the database name, mydb, is stored in the backup directory).
It will not overwrite or update existing documents, nor delete documents that are currently present but not present in the backup.
mongorestore --drop mydb.mongobackup
This will drop (i.e. delete) each collection before importing from the backup. This means that
However note that while importing the backup, some documents might be missing from the database until the backup has been fully restored.
Note that this will not drop collections that are not present in the backup.
Your C++ code contains a line like
#include <stringstream>
since you want to use std::stringstream, but your compiler gives you this error message:
main.cpp:2:10: fatal error: stringstream: No such file or directory
#include <stringstream>
^~~~~~~~~~~~~~
compilation terminated.
The header is called sstream, not stringstream! Use this #include directive instead:
#include <sstream>
This function converts any hex string like 55 to its equivalent decimal value:
#include <sstream>
#include <int>
unsigned int hexToDec(const std::string& str) {
unsigned int ret;
std::stringstream ss;
ss << std::hex << str;
ss >> ret;
return ret;
}e.g.
hexToDec("55"); // returns 85Note that while the code is somewhat concise, it might be neither the most performant nor the most concise option especially for developers that don’t really know std::stringstream.