if(player) versus while(player == 0)

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if(player) versus while(player == 0) #294136 10/16/09 14:52 10/16/09 14:52
Joined: Sep 2003 Posts: 5,900 Bielefeld, Germany Pappenheimer OP Senior Expert
Pappenheimer OP Senior Expert Joined: Sep 2003 Posts: 5,900 Bielefeld, Germany	Can anybody tell me, why the first thing works, but the latter not? The first is waiting while the pointer 'player' is empty. The second and third version tests whether 'player' is valid. What's wrong with that? Code: while(player == 0){wait(1);} while(1) { // if(player == 1) // { if(vec_dist(player.x, my.x) < 200) { sound(); } // } wait(1); } Code: //while(player == 0){wait(1);} while(1) { if(player == 1) { if(vec_dist(player.x, my.x) < 200) { sound(); } } wait(1); } Code: //while(player == 0){wait(1);} while(1) { if(player) { if(vec_dist(player.x, my.x) < 200) { sound(); } } wait(1); } http://www.puppenheim.org/ http://www.wuerfels-welt.de Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip http://www.puppenheim.org/blender_starting_main_settings.txt

Re: if(player) versus while(player == 0) [Re: Pappenheimer] #294146 10/16/09 15:54 10/16/09 15:54
Joined: Jan 2007 Posts: 1,619 Germany Scorpion Serious User
Scorpion Serious User Joined: Jan 2007 Posts: 1,619 Germany	player is a pointer and a pointer is invalid (=not set), if it's 0 (NULL). When it is set, then it becomes something different to zero and pretty unlikely exactly 1. And there is the mistake. A condition (as in a while or if) is false exactly then, when it's zero, if the variable has any other value it's true. you(player==1) will probably return false and so not execute the branch, because the variable is with a high probability not 1. Hope you got the point Scorpion

Re: if(player) versus while(player == 0) [Re: Scorpion] #294148 10/16/09 16:20 10/16/09 16:20
Joined: Sep 2003 Posts: 5,900 Bielefeld, Germany Pappenheimer OP Senior Expert
Pappenheimer OP Senior Expert Joined: Sep 2003 Posts: 5,900 Bielefeld, Germany	Thanks for your reply! Originally Posted By: Scorpion you(player==1) will probably return false and so not execute the branch, because the variable is with a high probability not 1. This was the reason, why I tried the third version: 'if(player)' - isn't any value above zero true? http://www.puppenheim.org/ http://www.wuerfels-welt.de Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip http://www.puppenheim.org/blender_starting_main_settings.txt

Re: if(player) versus while(player == 0) [Re: Pappenheimer] #294150 10/16/09 16:26 10/16/09 16:26
F Fear411 Unregistered
Fear411 Unregistered F	Try it like this: Code: while(1) { if(player != NULL) { if(vec_dist(player.x, my.x) < 200) { sound(); } } wait(1); }

Re: if(player) versus while(player == 0) [Re: ] #294152 10/16/09 16:46 10/16/09 16:46
Joined: Sep 2003 Posts: 5,900 Bielefeld, Germany Pappenheimer OP Senior Expert
Pappenheimer OP Senior Expert Joined: Sep 2003 Posts: 5,900 Bielefeld, Germany	Hm, it seems that all the trouble is because of my 'fuzzy' memory. I would enjoy to have a more precisely one. I tried your version, and my third again, and both worked - maybe a second mistake of mine interfered to make me think that it didn't work either. Sorry to have bothered you! Thanks! http://www.puppenheim.org/ http://www.wuerfels-welt.de Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip http://www.puppenheim.org/blender_starting_main_settings.txt