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eamtbfs

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[½»Á÷] ¡¾ÇóÖú¡¿°ïæ¿´¿´ÄÄ´íÁËerror: invalid lvalue in assignment

ÎÒ×î½üÓõ½FFTW£¬¾ÍÍøÉÏÕÒÁ˸ö¼òµ¥Àý×ÓÀ´Ñ§Ï°ÁËÏ¡£µ«Õâ¸ö¼òµ¥Àý×Ó±àÒë³ö´í£¬²»ÖªµÀÔõô»ØÊ¡£ÎÒÍøÉϲéÁ˲飬Ҳû¸ãÇåÊÇFFTWÓï¾äµÄÎÊÌ⣬»¹ÊÇgcc±àÒëÆ÷µÄÎÊÌâ¡£Çë¸ßÊÖ°ïæ¿´¿´°¡£¡

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$gcc34 FFTW_example.c -lfftw3 -lm
FFTW_example.c: In function `main':
FFTW_example.c:35: error: invalid lvalue in assignment
FFTW_example.c:36: error: invalid lvalue in assignment

ÓÃgcc4.3Ò²ÊÇÒ»Ñù³ö´í¡£

Õâ¸öFFTWµÄ¼òµ¥Àý×Ó³ÌÐòµÄÍøÖ·ÔÚÕâÀïhttp://www.elisanet.fi/mnentwig/webroot/FFTW_example/index.html

³ÌÐò±È½ÏС¾ÍÌùÔÚÏÂÃæ¡£ÊÇcreal ºÍcimagÄÇÁ½Ðгö´íÁË
/* ****************************************************
* FFTW example
* Markus Nentwig, 2007
* This program is in the public domain
* ****************************************************/
#include
#include
#include
#include
#include

int main(void){
  /* ****************************************************
   * Allocate memory
   * ****************************************************/
  int n=128;
  fftw_complex* b1=fftw_malloc(sizeof(fftw_complex)*n);
  fftw_complex* b2=fftw_malloc(sizeof(fftw_complex)*n);

  /* ****************************************************
   * Create forward FFT plan from b1 into b2
   * ****************************************************/
  fftw_plan p1=fftw_plan_dft_1d(n, b1, b2, FFTW_FORWARD, FFTW_ESTIMATE);

  /* ****************************************************
   * Create reverse FFT plan from b2 into b1
   * ****************************************************/
  fftw_plan p2=fftw_plan_dft_1d(n, b2, b1, FFTW_BACKWARD, FFTW_ESTIMATE);

  /* ****************************************************
   * Generate a single sine wave cycle
   * ****************************************************/
  int i;
  for (i=0; i < n; ++i){
    creal(b1)=sin((double)i/(double)n*2.0*M_PI);
    cimag(b1)=0;
  }
  
  /* ****************************************************
   * Execute FFT from b1 into b2
   * ****************************************************/
  fftw_execute(p1);

  /* ****************************************************
   * Dump the "spectrum".
   * Result:
   * First bin ("DC  term" is zero
   * * i*n/2 in 2nd bin
   * * -i*n/2 in last bin
   * * all other bins are zero
   * ****************************************************/
  for (i=0; i < n; ++i){
    printf("%1.7f\t%1.7f\n", creal(b2), cimag(b2));
  };

  /* ****************************************************
   * IFFT back into b1
   * ****************************************************/
  fftw_execute(p2);
  printf("\n";

  /* ****************************************************
   * Result: Original waveform scaled by n
   * ****************************************************/
  for (i=0; i < n; ++i){
    printf("%1.7f\t%1.7f\n", creal(b1), cimag(b1));
  };

  /* ****************************************************
   * Clean up
   * ****************************************************/
  fftw_destroy_plan(p1);
  fftw_destroy_plan(p2);

  fftw_free(b1);
  fftw_free(b2);
  return 0;
}
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¡ï ¡ï ¡ï
eamtbfs(½ð±Ò+1): лл²ÎÓë 2011-02-25 06:01:14
ÓàÔó³É(½ð±Ò+3): лл²ÎÓëÓ¦Öú£¡ 2011-02-27 15:06:29
³­¶¼Ã»³­¶Ô¿©
CODE:
    creal(b1[i])=sin((double)i/(double)n*2.0*M_PI);
    cimag(b1[i])=0;

CODE:
printf("%1.7f\t%1.7f\n", creal(b1[i]), cimag(b1[i]));

2Â¥2011-02-24 19:31:36
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû

eamtbfs

Í­³æ (СÓÐÃûÆø)


zzzzz

[ Last edited by eamtbfs on 2011-2-25 at 06:06 ]
3Â¥2011-02-25 06:04:26
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eamtbfs

Í­³æ (СÓÐÃûÆø)


ÒýÓûØÌû:
Originally posted by yalefield at 2011-02-24 19:31:36:
³­¶¼Ã»³­¶Ô¿©
CODE:
    creal(b1[i])=sin((double)i/(double)n*2.0*M_PI);
    cimag(b1[i])=0;

CODE:
printf("%1.7f\t%1.7f\n", creal(b1[i]), cimag(b1[i]));


ÎÒ´ÓÍøÒ³ÉÏÌû¹ýÀ´µÄ£¬²»ÖªÔõôÌù¹ýÀ´¾Í±äÁË¡£²»¹ýÎÒ±àÒëµÄʱºòÊÇÓõÄÍøÉÏÏÂÔØµÄ³ÌÐò£¬ÎÒ×Ðϸ¿´ÁË£¬ÎÒ±àÒëµÄ³ÌÐòÓ﷨ûÓÐÕâÑùµÄ´í£¬µ«¾ÍÊÇgcc±¨¸æerror: invalid lvalue in assignment

Çë°ïæ±àÒëÏ£¬¿´¿´ÎÊÌâ³öÔÚÄÄ¡£¶àл¶àл£¡
4Â¥2011-02-25 06:05:21
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lucktroy

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¡ï ¡ï ¡ï
ÓàÔó³É(½ð±Ò+3): лл²ÎÓëÓ¦Öú£¡ 2011-02-28 20:09:22
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5Â¥2011-02-28 19:25:46
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holmescn

½ð³æ (ÕýʽдÊÖ)


¡ï ¡ï
ÓàÔó³É(½ð±Ò+2): лл²ÎÓëÓ¦Öú£¡ 2011-03-07 21:38:09
ûÓùýFFTW£¬²»¹ýÕâÁ½ÐÐȷʵ±È½ÏÆæ¹Ö
CODE:
  /* ****************************************************
   * Generate a single sine wave cycle
   * ****************************************************/
  int i;
  for (i=0; i < n; ++i){
    creal(b1[i])=sin((double)i/(double)n*2.0*M_PI);
    cimag(b1[i])=0;
  }

crealºÍcimagÊÇÁ½¸öº¯Êý»¹ÊÇÁ½¸öºê°¡¡£Èç¹ûÊÇÁ½¸öº¯Êý£¬ÄÇÕâÀï¿Ï¶¨ÊÇÓÐÎÊÌâµÄ¡£Èç¹ûÊÇÁ½¸öºê£¬²»ÖªµÀ»áÕ¹¿ª³Éʲô¡£
6Â¥2011-03-04 09:46:57
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magic7004

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7Â¥2011-03-08 16:00:08
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