----------------------------------- xX_MayDay_Xx Mon Mar 20, 2006 8:25 am Math.abs ----------------------------------- ok....i know that Math.abs gives the absolute value of a number..ex(the absolute value of -12...is..12) put i need to know how to do this without using the Math.abs application....i think it has something to do with multipling the number by it's self then dividing by 2? ----------------------------------- Andy Mon Mar 20, 2006 8:26 am ----------------------------------- how about give us the definition of absolute value, once you understand what it means, this question becomes intuitive ----------------------------------- xX_MayDay_Xx Mon Mar 20, 2006 8:37 am ----------------------------------- yeah.....i was an idiot......basic rule of math....anything *1 equals its self...that combined with the rules of integers -*+=-....or -*-=+...thats all had to do....i was an idiot...i will no freely except harassment for the uber n()()b... public class AbsoluteValue { public static void main(String[]args) { int num; System.out.println("please enter a number"); num=In.getInt (); if (num>=0) { System.out.println("the absolute value of that number is..." + num); } else { System.out.println("the absolute value of "+num+" is..." +num*-1); } } } ----------------------------------- Andy Mon Mar 20, 2006 8:40 am ----------------------------------- there ya go :) ----------------------------------- xX_MayDay_Xx Tue Mar 21, 2006 8:32 am ----------------------------------- ummm....whats a switch application? ----------------------------------- Krabjuice Tue Mar 21, 2006 2:43 pm ----------------------------------- Something that uses the switch statement, i'd assume. Switch is a "in the case of" type of control sequence. People generally use if's, but switch has it's uses. ----------------------------------- Dan Tue Mar 21, 2006 3:13 pm ----------------------------------- I think the most effsent way of doing this whould be to set the singed bit to 0 or what ever means postive on your cpu. Tho this whould probly be a bit complicated for most peoleop and is not real high level progaming but rather low level asm type stuff. I guse this is what Math.abs is for =p. ----------------------------------- md Tue Mar 21, 2006 4:10 pm ----------------------------------- I dunno dan; getting a single bit isn't easy; I think a strait compare might be faster n is $2 $3 is temporary storage compare: bgtz $2, ret addi $3, $0, -1 mult $2, $3 mflo $2 ret: bit-wise addi $3, $3, 0 sra $3, $3, 31 bne $3, $0, ret addi $3, $0, -1 mult $2, $3 mflo $2 ret: ----------------------------------- Dan Tue Mar 21, 2006 6:40 pm ----------------------------------- I am prity shure that in asm at least seting one byte to 0 with a mov instruction is faster. ----------------------------------- md Tue Mar 21, 2006 6:47 pm ----------------------------------- Wha? I'm using words... and I don't set any to zero.. setting the sign bit to 0 instead of 1 would not change the sign of the number at all, it would radically change the number though. 1110 + 0010 = 0000. 0010 is the positive number, 1110 is it's negative. 0110 + 0010 = 1000, clearly not zero ;) ----------------------------------- rizzix Wed Mar 22, 2006 3:17 pm ----------------------------------- 1101 & 0111 = 0101 ^-- sign bit I believe that's what Dan was aiming for. ----------------------------------- md Wed Mar 22, 2006 4:21 pm ----------------------------------- yeah, but just checking it is still slow. It's best case two instructions to compare just hte bit, whereas a simple less then is only one. ----------------------------------- rizzix Wed Mar 22, 2006 5:39 pm ----------------------------------- 1101 & 0111 = 0101 ^-- sign bit / resut is a positive number: 0xxx 0110 & 0111 = 0110 ^-- sign bit / result is a positive number 0xxx :) It is fast. But as we discussed in #compsci.ca it isin't actually the case. Two's complement is a whole lot trickier than just fixing one bit.