Funny C tricks

Taken from Bill Rowan's Stanford ACM presentation:

The "downto" operator:

int main()
{
int i = 5;
while(i --> 0) // --> is the downto operator!
{
  printf("%d\n", i);
}
return 0;
}

Cast any type to "bool" type (that is, 1 or 0):

!!foo

"Computed goto" (compiler-dependent && unary operator):

void print_loop(int s, int e) {
 assert(s < e);   
 top:    
 printf("%d\n", s);  
 goto *( &&top + ( !!(s++/e) ) * ( &&end - &&top ) );    
 end:  
 ;
} 

VIM (and some vi)

Everybody who knows me knows that I love vim. Vim is a powerful version of the vi editor. It usually comes with any *NIX instillation. It rules. Here are some links, and some of my favorite (non-obvious) tricks. If you are new to all of this, a good place to start is the VI lovers home page or, if you are in a hurry, the quick reference card.

VIM

• VIM home page
• VIM quick reference card
• VIM syntax highlighting HOWTO and more
• AWESOME page on VIM regular expressions
• VIM web ring
• Using ISpell with VIM
• Dr. Chip's VIM page -- useful stuff and lots of links

Plain old VI

• VI lovers home page
• Cult of VI
• Wikipedia VI page

Tricks

• Swap two characters xp
• Swap two lines ddp
• Reverse the order of all lines :g/^/m0/
• Remove all lines with only whitespace :g/^\s*$/d
• Move all lines onto one logical line :%j
• Remove all blank lines :g/^$/d
• Insert a newline at the end of every line :%s/$/^m/ (keystrokes to get this one are: Ctrl+V, Ctrl+M)
• Text completion before, after cursor: Ctrl+N, Ctrl+P (thanks to neha for this link )
• Get a command prompt :shell
• Execute a shell command :!<command>
• Append the contents of a file into your vi session :r!cat <file>
• Omni-completion Ctrl+X Ctrl+O
• Whole line completion Ctrl+X Ctrl+L
  
• Search for a word forward under the cursor *
• Search for a word backwards under the cursor #
• Move to a percentage of the file: type the number, then hit %