acs17111@uop.edu (hamid misnan) (09/20/90)
Hai, Can someone help me in how can I swap bit 2 and 5, I had tried to use bitwise, but I cannot finger it out how it will work. Any help will be appreciated. Thanks in advance.
browns@iccgcc.decnet.ab.com (Stan Brown, Oak Road Systems) (09/21/90)
In article <26f8528c.35c1@uop.uop.edu>, acs17111@uop.edu (hamid misnan) writes: > Hai, > Can someone help me in how can I swap bit 2 and 5, I had tried > to use bitwise, but I cannot finger it out how it will work. > Any help will be appreciated. > Thanks in advance. sometype swap_bits_2and5(sometype mumble) { sometype bit2, bit5; bit2 = mumble & (sometype)0x04; bit5 = mumble & (sometype)0x20; return (mumble ^ (bit2|bit5)) | (bit2<<3) | (bit5>>3); } Depending on the actual type of the value, some of those casts may not be necessary. And now, inquiring minds want to know: Why on earth do you want to do this? -- Stan Brown, Oak Road Systems, Cleveland, Ohio, U.S.A. (216) 371-0043 Disclaimer: Your mileage may vary. Close cover before striking. Void where taxed, regulated, licensed, or prohibited by law. I am not a crook.
kaiser@ananke.stgt.sub.org (Andreas Kaiser) (09/21/90)
In a message of <Sep 20 05:24>, hamid misnan (acs17111@uop.edu ) writes:
hm> Can someone help me in how can I swap bit 2 and 5, I had tried
hm> to use bitwise, but I cannot finger it out how it will work.
hm> Any help will be appreciated.
hm> Thanks in advance.
#define Bit(n) (1 << (n))
i = (i & ~(Bit(2)|Bit(5))) | (i & Bit(5)) >> 5-2 | (i & Bit(2)) << 5-2;
--
:::::::::::::::::::: Internet: kaiser@ananke.stgt.sub.org
:: Andreas Kaiser :: Fidonet: 2:507/18.7206 (+ 2:509/5.2512)
::::::::::::::::::::roger@everexn.com (Roger House) (09/22/90)
In <26f8528c.35c1@uop.uop.edu> acs17111@uop.edu (hamid misnan) writes: >Hai, > Can someone help me in how can I swap bit 2 and 5, I had tried > to use bitwise, but I cannot finger it out how it will work. > Any help will be appreciated. > Thanks in advance. The possible transformations are these: 543210 ---------------------- 0xx0xx -> no change 0xx1xx -> 1xx0xx 1xx0xx -> 0xx1xx 1xx1xx -> no change Say B is the variable for which bits 2 and 5 are to be swapped. Then this code will do the trick, although it requires the use of another variable, t: if ((t = B & 0x24) && t != 0x24) /* Swap bits 2 and 5 of B */ B ^= 0x24; There are probably better ways to do it. Roger House
dmi@peregrine.peregrine.com (Dean Inada) (09/22/90)
In article <26f8528c.35c1@uop.uop.edu> acs17111@uop.edu (hamid misnan) writes: > Can someone help me in how can I swap bit 2 and 5, I had tried /* Ask a silly question... :-) */ #define swap25(x) ((((x)*01000001001)&04000040733)%07777) /* Note: this assumes x fits in 9 bits */
george@hls0.hls.oz (George Turczynski) (09/26/90)
In article <1990Sep21.182142.9013@everexn.com>, roger@everexn.com (Roger House) writes: [...Deleted...] > > Say B is the variable for which bits 2 and 5 are to be swapped. Then this > code will do the trick, although it requires the use of another variable, > t: > > if ((t = B & 0x24) && t != 0x24) /* Swap bits 2 and 5 of B */ > B ^= 0x24; > > There are probably better ways to do it. > Well, to do a similar thing without the use of a temporary, try this: B= !!(B&0x20)^!!(B&0x4) ? B^0x24 : B; This follows from your truth table (that I deleted), as the result is only different if bits 5 and 2 are different (which is what the curious looking test, !!(B&0x20)^!!(B&0x4), finds out). -- George P. J. Turczynski, Computer Systems Engineer. Highland Logic Pty Ltd. ACSnet: george@highland.oz |^^^^^^^^^^^^^^^^^^^^^^^^| Suite 1, 348-354 Argyle St Phone: +61 48 683490 | Witty remarks are as | Moss Vale, NSW. 2577 Fax: +61 48 683474 | hard to come by as is | Australia. --------------------------- space to put them ! ---------------------------