C++ sin() returns incorrect results -

-

i have piece of code

bool position::hasinline(const unit * const target, float distance, float width) const {     if (!hasinarc(m_pi, target) || !target->iswithindist3d(m_positionx, m_positiony, m_positionz, distance))         return false;     width += target->getobjectsize();     float angle = getrelativeangle(target);     float abssin = abs(sin(angle));     return abs(sin(angle)) * getexactdist2d(target->getpositionx(), target->getpositiony()) < width; }

problem ran is, when debug gdb , try "p sin(angle)" returns weird values - angle 1.51423 states sin = 29 (so yes, putting in radians :-) ). more weird is, when try "p abssin" returns 0, , yes, on next line, "float abssin = abs(sin(angle))" line done. originaly there wasnt included cmath, m_pi const returning correct value, though added #include @ start of .cpp file make sure, nothing changed.

if helps, im using linux kernel 2.6.26-2-xen-amd64 ideas?

the function abs (as defined in cstdlib) takes integer , returns integer. when dealing doubles, should using fabs instead.

another version of abs defined in cmath (#include <cmath>). overloaded accept (and return) both integers , doubles.

you may wish double-check version using.


Comments

Post a Comment

Popular posts from this blog

javascript - Enclosure Memory Copies -

-
function myclass() { //lots , lots of vars , code here. this.bar = function() { //do numerous enclosed myclass vars } this.foo = function() { alert('hello'); //don't enclosed variables. } } each instance of myclass gets own copy of bar , foo, why prototyped methods use less memory. however, know more memory use of inner methods. it seems obvious me (1) below must true. agree? not distinct myclass instances have own distinct copies of bar, must have own distinct copies of myclass enclosure. (or else how bar method keep myclass variables straight on per instance basis?) now (2) question i'm after. since inner foo method doesn't use in myclass enclosure natural qustion is: javascript smart enough not keep myclass enclosure in memory use of foo? this depend entirely on implementation not language. naive implementations keep far more around others. answer true e.g. v8 (chrome's js engine) may not true spider...
Read more

php - Replacing tags in braces, even nested tags, with regex -

-
example preg_replace('/\{[a-za-z.,\(\)0-9]+\}/', 'replaced', 'lorem ipsum dolor sit {tag1({tag2()})}, consectetur adipiscing elit.'); the result: lorem ipsum dolor sit {tag1(replaced)}, consectetur adipiscing elit. question as can see "tag2" has been replaced, want replace "tag1" know how can this? (in cases might this: {tag1({tag2({tag3()})})}) , on.) btw using preg_replace_callback, easier show preg_replace here site can test code: http://www.spaweditor.com/scripts/regex/index.php you need add curly braces character set. here's pattern used: /\{[a-za-z.,\(\)\{\}0-9]+\}/ and here result: "lorem ipsum dolor sit replaced, consectetur adipiscing elit."
Read more