decrement

Confusion with ++ and -- operator int a = 10; printf("%d\n", -(--a) ); // valid output: -9 But, problem occurs when following is used: printf("%d\n", --(-a)); // error, invalid Why? The ++ and -- operator works on only lvalue, not value. An lvalue is something that can stand on the left side of an assignment. printf("%d\n", -(--a) ); Here, -- operator works on variable a , so this is valid. But, printf("%d\n", --(-a)); Here, (-a) returns a value. -- is applied to a value, which is not valid. This is because -- modifies a variable, and int value can't be modified (For example you can't do 7 = 5

What is the idiomatic Common Lisp way to increment/decrement numbers and/or numeric variables? Use the built-in "+" or "-" functions, or their shorthand "1+" or "1-", if you just want to use the result, without modifying the original number (the argument). If you do want to modify the original place (containing a number), then use the built-in "incf" or "decf" functions. Using the addition operator: (setf num 41) (+ 1 num) ; returns 42, does not modify num (+ num 1) ; returns 42, does not modify num (- num 1) ; returns 40, does not modify num (- 1 num) ; NOTE: returns -40, since a - b is not

I know how to do a incrementing for loop in coffeescript such as: Coffeescript: for some in something Generated Javascript: for (_i = 0, _len = something.length; _i < _len; _i++) How do I create a decrementing for loop similar to this in Coffeescript? for (var i = something.length-1; i >= 0; i--) Trevor Burnham EDIT: As of CoffeeScript 1.5 by -1 syntax is supported. First, you should familiarize yourself with the by keyword, which lets you specify a step. Second, you have to understand that the CoffeeScript compiler takes a very naïve approach to loop endpoints (see issue 1187 , which Blender

Why do the x86 instruction INC (increment) and DEC (decrement) not affect the CF (carry flag) in FLAGSREGISTER? Ira Baxter To understand why you probably need to remember the current "x86" CPUs with 32 and 64 bit values started life as much more limited 8-bit machines, going back to the Intel 8008. (I coded in this world back in 1973, I still remember (ugh) it!). In that world, registers were precious and small. You need INC / DEC for various purposes, the most common being loop control. Many loops involved doing "multi-precision arithmetic" (e.g, 16 bits or more!) By having INC / DEC set the

I have this piece of code (taken from this question ): var walk = function(dir, done) { var results = []; fs.readdir(dir, function(err, list) { if (err) return done(err); var pending = list.length; if (!pending) return done(null, results); list.forEach(function(file) { file = path.resolve(dir, file); fs.stat(file, function(err, stat) { if (stat && stat.isDirectory()) { walk(file, function(err, res) { results = results.concat(res); if (!--pending) done(null, results); }); } else { results.push(file); if (!--pending) done(null, results); } }); }); }); }; I'm trying to follow it, and I think I

Consider following piece of code void foo( bool forwad ) { vector<MyObject>::iterator it, end_it; int dir; it = some_global_vector.begin() + some_position; if( forward ) { dir = 1; it += 1; end_it = some_global_vector.end(); } else { dir = -1; it -= 1; end_it = some_global_vector.begin()-1; } while( it != end_it ) { if( do_domething() ) break; it += dir; } } As you can see there is some doubt when forward == false becouse there is an substraction from begin() and iterator it can be substracted when it points at begin() . I can't find anywhere if it is ok until I not dereference this bad