We know compilers like gcc can do lots smart optimization to make the program run faster. Regarding functions call optimization, gcc can do tail-call elimination to save the cost of allocating a new stack frame, and tail recursion elimination to turn a recursive function to non-recursive iterative one. gcc can even transform some recursive functions
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Tag: Programming
Bash Learning Materials
Posted onBash (GNU Bourne-Again SHell) the default shell for many Linux distributions. It is very common for scripting languages in Linux. Bash is easy and straightforward for writing small tools. However, as most tools, it has its grammars that could easily cause bugs if they are not used correctly. Here I summarize a list of good
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How to Install Wine 32-bit on CentOS 8
Posted onSince version 7, RHEL and CentOS only have 64 bit versions. For some reasons, it’s better to run many Windows applications under 32 bit wine. Like How to Install Wine 32-bit on CentOS 7, this post introduce how to install 32-bit Wine on CentOS 8. Most of the mechanisms are similar yet there are differences.
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How to Convert Integers to Strings and Strings to Integers in PHP
Posted onConversion from integer to string and from string to integer are common operations in most applications such as C++. PHP has its uniqueness in language and standard library design. In this post, we will check methods to convert integers to strings and vice versa. Convert string to int in PHP You can cast a string
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A StoneWall Solution in C++
Posted onStoneWall is an interesting problem that requires some brain cycles yet not too complex. It is good software engineer interview question. Here is a C++ solution whose complexity is O(N). #include <stack> int solution(std::vector<int> &H) { int stones = 0; std::stack<int> heights; for (auto h: H) { while (!heights.empty() && h < heights.top()) { heights.pop();
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How to Statically Link OCaml Programs
Posted onStatic linking is preferred for some cases although it has its own various problems. Static building/linking is not always possible for some languages on some platform. For OCaml, the answer to this question is yes. In this post, we will introduce 2 methods to statically linking OCaml: static linking with runtime glibc required and static
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5 necessary PC hardware that a programmer needs to upgrade
Posted onThe world of technology has evolved drastically over the last few decades. Almost every aspect of our lives is dominated by technology. At the heart of technology lies computer programming. Computer programming is what dictates the success of the technology. I mean think about it, your smartphone, PC, ETC they all rely on programming. This
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New Linux Kernel 5.0: Features and Improvements
Posted onLinux is the most used and well-known open-source operating system for computers, mobile devices, servers, and mainframes, etc. Linux has so many awesome features to serve its users like Live CD/USB. And it is fast, easy and free to use by computers around the world. The kernel is referred to as the essential component of
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How to write file content with sudo in Vim?
Posted onVim opens file even if the user does bot have write permission to the file. But after revision, how to write file content with sudo in Vim if Vim reports no permission to write the file. Use this command inside of vim to write to the file with sudo: :w !sudo tee % Here, !
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What can we expect in Java update 2019?
Posted onJava is the most regularly used programming language for the creation of web applications. This high-level programming language develops by the Sun Micro-system. This language was designed for use in the world of internet and known for fastest, secure, and most reliable language of the computing platform. One interesting fact is that Java programmers are
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Installing Zlib Library in Ubuntu Linux
Posted onOn Ubuntu (18.04 and 20.04), installing zlib reported unable to locate package zlib: $ sudo apt install zlib Reading package lists… Done Building dependency tree Reading state information… Done E: Unable to locate package zlib How to install zlib in Ubuntu? Install zlib in Ubuntu from Ubuntu package repo In Ubuntu, the zlib package is
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Handling Sparse Files on Linux
Posted onSparse files are common in Linux/Unix and are also supported by Windows (e.g. NTFS) and macOSes (e.g. HFS+). Sparse files uses storage efficiently when the files have a lot of holes (contiguous ranges of bytes having the value of zero) by storing only metadata for the holes instead of using real disk blocks. They are
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gdb like step by step debugger for Python
Posted onAny good debugger for Python that is like gdb so that the code can be executed step by step for debugging purpose? You might check pdb. You can debug a program such as prog.py by invoking it through pdb: python -m pdb prog.py Common gdb commands can be found in pdb: (Pdb) h Documented commands
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How to get the full path and directory of a Python script itself?
Posted onIn a Python script, how to get the full path and directory of the Python script itself? To get the path of the current file (the script itself), you can use __file__. To resolve any symbolic links in the path, you can use os.path.realpath(). Putting them together, you can do os.path.realpath(__file__) to get the full
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How to test a file or directory exists in C++?
Posted onHow to test a path (a file or directory exists) in C++? In Bash, the [ -f ] and [ -d ] tests can test whether a file or a directory exist. What are the corresponding C++ ways for these tests? To test whether a file or dir (a path) exists, you may call stat()
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How to create a file if not exist and open it in read and write modes in C++?
Posted onHow to create a file if not exist and open it in read and write modes in C++? For example, I would like open a fstream on /tmp/cache to be able to read it and append to it. If the file does not exist yet, create one. A simple code like std::fstream fs(“/tmp/cache”, std::ios::in |
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How to test whether a file exists and is a block special file in Python on Linux?
Posted onBash has a -b test to test whether a file exists and is a block special file. -b file True if file exists and is a block special file. How to do this in Python? Python’s stat module provides the similar functions for the C standard APIs and macros underlining such as stat() and S_ISBLK().
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How to not use concrete types in lambda function parameters in C++11?
Posted onC++11 requires that lambda function parameters be declared with concrete types. This is sometimes annoying. auto is really nice, especially when the type is complex like std::vector<std::string>::iterator is quite long to type. I know C++14 allows auto in lambda functions. But how to not use concrete types in lambda function parameters in C++11? In C++11,
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How to escape special characters in a Bash string in Linux?
Posted onThe problem is with ssh that makes a quoted string to more than one if there are spaces. For example, ssh user@host cmd “my string” The cmd on host will be executed like cmd my string rather than cmd “my string” It will only work if the string is escaped like ssh user@host cmd my
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How to check whether a string starts with another string in C++?
Posted onHow to check whether a string starts with another string in C++? For example, startwith(“big string here…”, “big”) –> True and startwith(“big string here…”, “small”) –> False and startwith(“big”, “big string here”) –> False The std::string::compare() standard library function of C++ can be used. int compare( size_type pos1, size_type count1, const basic_string& str ) const;
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