[Solved] Converting C code to Java [closed]

double* ptr; ptr = (double*)malloc(10*_R_CONST*sizeof(double)+2048); This is the C way of allocating an array dynamically at runtime, the Java equivalent is double[] ptr = new double[10*_R_CONST+256]; (Note that Java does not need the sizeof(double) factor, since it allocates objects, not bytes. For the same reason, the 2048 byte buffer shrinks to 256 doubles.) Similar, the … Read more

[Solved] Does ccall really convert arguments passed by pointer?

This turned out to be either a bug in the core library or a very misguided documentation, depending on the perspective (issue #29850). The behavior of the function unsafe_convert changed from version 0.4 to 0.5, in a way that makes it more flexible than what is currently suggested. According to this commit, unsafe_convert changed from … Read more

[Solved] What does null pointer exception mean in error messages? [duplicate]

Java doesn’t use pointers, but uses references. NullPointerException is a way to say that an attempt is made to send a message (invoke a method) using reference which doesn’t point to any object. It has nothing to do with pointers in the sense of C/C++. solved What does null pointer exception mean in error messages? … Read more

[Solved] Difference between std::string [] operator and at()

Your second program is malformed. It’s not using std::string::operator[] at all. string * ps = new string(str); ps[0] = ‘n’; Not only does std::string support the [] operator, every pointer to a type also supports the [] operator. It’s how C style arrays work, and it’s what you’re doing in the code above. ps isn’t … Read more