Problem:
You encounter a GCC error message of the form
error: default argument for parameter of type <some type> has type <some other type>
03
Feb
2013
Programming languages
11
Jan
2013
C++: Check if file exists
Problem:
In C++ you want to check if a given file exists, but you can’t use stat() because your code needs to work cross-plaform.
11
Jan
2013
Enable Menu-Style Autocompletion in ZSH
Problem:
You have installed zsh but you don’t see the menu-style autocompletion (where you can navigate the suggestions using the arrow keys on the keyboard)
02
Jan
2013
A text-to-Brainfuck/RNA converter in ANSI C99
Brainfuck encoder
The following small ANSI C99 program reads a String from stdin and prints out a Brainfuck program that prints the same String on stdout.
Compile using gcc -o bf bf.c
Use it like this:
cat my.txt | ./bf > my.bf
Source code:
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv) {
unsigned char c;
unsigned char curval = 0;
//Initialize reg+1 with 8
while(1) {
c = getchar();
if(feof(stdin)) {break;}
while(curval != c) {
if(curval < c) {
putchar('+');
curval++;
} else if(curval > c) {
putchar('-');
curval--;
}
}
putchar('.');
}
}How does it work?
Basically it uses just one of the registers of the Brainfuck Turing machine and incremets or decrements the register to be able to print out the next byte. It doesn’t use any of the more ‘advanced’ features in Brainfuck like loops.
08
Dec
2012
Shell: Strip directory from path
Problem:
In the Linux shell, you have a file path and you want to strip everything but the filename, for example you have the path ../images/photo.jpg and want only photo.jpg
07
Dec
2012
Finding the maximum line length of a file in Ruby
23
Nov
2012
Othello in Java: Part 1: Data structures
You’ve got a big problem. Someone forces encourages you to implement a complete Othello UI+AI in Java, but you don’t have any idea how to do that. If you already know how to implement the basics and you are interested in more advanced strategy concepts, you might be interested in the other parts of this series (yet to come).
In this multi-part series I will not provide any complete solution to any of the standard Othello tasks. Instead, I will provide (hopefully) helpful hints how to get your coding going and explain how your code works.
22
Nov
2012
Convert ZIP to TAR using Linux shell
Problem
You have ZIP archive and want to convert it to TAR automatically conserving the original directory structure.
22
Nov
2012
Strip extension from filename in bash/zsh
Problem:
You have a filename in the Linux shell and want to strip/remove the filename extension from it – e.g. if you have myarchive.zip, you want to get only myarchive as output.
20
Nov
2012
C/C++ Base64 codec using libtomcrypt
Problem:
In C/C++ you want to encode/decode something from/to Base64. libtomcrypt is WTFPL-licensed and therefore provides a good choice for both commercial and non-commercial projects.
19
Nov
2012
Calculating cryptographic hashes using libtomcrypt in C/C++
Problem:
You want to calculate a hash of any string in C/C++. LibTomCrypt is WTFPL licensed, so it’s a good choice for commercial and non-commercial projects.
10
Nov
2012
R: Count occurrences of character in string
Problem
In GNU R, you have an arbitrary string s and want to count how often a given character occurs in s.
27
Oct
2012
LaTeX Tabular Column with specific font type
Problem:
You want to use a custom column type for your LaTeX tabular that has a specific font attribute (we’ll use the font family for this example).
23
Oct
2012
How to include Java sources in Maven JAR
Problem
You’re using Maven as build system but you need to include your Java sources into your JAR file generated by mvn package.
23
Oct
2012
Check Scanner number input boundary in Java
In many cases if you want to create an interactive command line interface, you need to check if a number entered by the user is valid and – if it isn’t – you want the user to re-input it.
Here’s a simple static method to check if a number typed by a user is within a given boundary:
/**
* Lets the user input an integer value until it satisfies the given
* conditions
*
* @param msg The prompt to ask the user for the value.
* @param lower The lower boundary, inclusive
* @param upper The upper boundary, inclusive
*/
private static int guardedInput(String msg, int lower, int upper) {
Scanner scanner = new Scanner(System.in);
while (true) {
System.out.print(msg);
int val = -1;
try {
val = scanner.nextInt();
} catch (InputMismatchException ex) {
System.out.println("Illegal value: Please type a number!");
}
if (val < lower) {
System.out.println("Illegal value: Must be greater than " + (lower - 1));
} else if (val > upper) {
System.out.println("Illegal value: Must be smaller than " + (upper + 1));
} else {
return val;
}
}
}
07
Oct
2012
How to fix npm “Cannot find module ‘graceful-fs'” error
Problem:
When running any npm command, you get a stacktrace similar to the following:
Error: Cannot find module 'graceful-fs' at Function.Module._resolveFilename (module.js:338:15) at Function.Module._load (module.js:280:25) at Module.require (module.js:362:17) at require (module.js:378:17) at Object.<anonymous> (/usr/share/npm/lib/utils/ini.js:32:10) at Module._compile (module.js:449:26) at Object.Module._extensions..js (module.js:467:10) at Module.load (module.js:356:32) at Function.Module._load (module.js:312:12) at Module.require (module.js:362:17)
05
Oct
2012
How to fix node-waf “ImportError: No module named Scripting” on Linux
Issue:
When executing node-waf, you get the following error message:
Traceback (most recent call last): File "/usr/local/bin/node-waf", line 14, in <module> import Scripting ImportError: No module named Scripting
This also prevents node modules with native components to be built.
17
Sep
2012
C++11 : Iterate over smart pointers using foreach loop
Problem:
In C++11 you want to iterate over a smart pointer (auto_ptr, shared_ptr, …). collection, say a std::vector, using the new for loop syntax.
Let’s try it out:
using namespace std;
shared_ptr<vector<int> > smartptr(/* A ptr to your vector */);
for(int s : smartptr) {
/* do something useful */
}When trying to compile this code, GCC emits the following error message (other lines are omitted for the sake of simplicity)
error: no matching function for call to 'begin(std::shared_ptr<std::vector<int> >&)' error: no matching function for call to 'end(std::shared_ptr<std::vector<int> >&)'
or, when LANG=de is set:
Fehler: keine passende Funktion für Aufruf von »begin(std::shared_ptr<std::vector<int> >&)« Fehler: keine passende Funktion für Aufruf von »end(std::shared_ptr<std::vector<int> >&)«
16
Sep
2012
Automatically format size string in Node.js
Problem:
In NodeJS, you got a size of a file in bytes, but you want to format it for better readability.
For example, if your size is 10000 bytes, you want to print 10 kilobytes, but if it is 1200000, you want to print 1.20 Megabytes.
16
Sep
2012
How to get filesize in Node.js
To determine the size of a file in NodeJS (e.g. to get the size of myfile.txt) use fs.stat() or fs.statSync() like this:
const fs = require("fs"); //Load the filesystem module
const stats = fs.statSync("myfile.txt");
const fileSizeInBytes = stats.size;
//Convert the file size to megabytes (optional)
const fileSizeInMegabytes = fileSizeInBytes / 1000000.0;Another option is to use the following function:
function getFilesizeInBytes(filename) {
const stats = fs.statSync(filename);
const fileSizeInBytes = stats.size;
return fileSizeInBytes;
}