error: array subscript is not an integer

Question

 int row,col,i,j,tmp1,tmp2,tmp3,tmp4,tmp5,tmp6,tmp7;
 if(M==64&&N==64){
    for(row=0;row<N;row+=8){
        for(col=0;col<M;col+=8){
             for(j=0;j<2;j++){
                for(i=row;i<row+4;i++){
                    tmp0=A[i+4j][col+0];
                    tmp1=A[i+4j][col+1];
                    tmp2=A[i+4j][col+2];
                    tmp3=A[i+4j][col+3];
                    tmp4=A[i+4j][col+4];
                    tmp5=A[i+4j][col+5];
                    tmp6=A[i+4j][col+6];
                    tmp7=A[i+4j][col+7];

                    B[col+0+4j][i]=tmp0;
                    B[col+1+4j][i]=tmp1;
                    B[col+2+4j][i]=tmp2;
                    B[col+3+4j][i]=tmp3;
                    B[col+0+4j][i+4]=tmp4;
                    B[col+1+4j][i+4]=tmp5;
                    B[col+2+4j][i+4]=tmp6;
                    B[col+3+4j][i+4]=tmp7;

                }

but I got the code the error: array subscript is not an integer. But I don't know why. Could someone have a look at and tell me why? I do not think I use other type in the array besides int.

Replace all those 4j with 4*j and try again.

Lee Duhem
– Lee Duhem

2014-02-27 10:25:42 +00:00
Commented Feb 27, 2014 at 10:25 — Lee Duhem
– Lee Duhem, Commented Feb 27, 2014 at 10:25
What is 4j in all those lines?

Sadique
– Sadique

2014-02-27 10:25:48 +00:00
Commented Feb 27, 2014 at 10:25 — Sadique
– Sadique, Commented Feb 27, 2014 at 10:25

unwind · Accepted Answer · 2014-02-27 10:37:16Z

3

C does not support implicit multiplication like you commonly see in math. It obviously wouldn't work, since variable names can be more than one letter, it would create a huge amount of parsing confusion.

By your (implied) logic, an expression such as row < N should then be the same as r * o * w < N, which is clearly not what you really think.

Thus, multiplication must always be done explicitly using the * binary operator: 4j is a parse error, you meant 4 * j.

edited Feb 27, 2014 at 10:37

answered Feb 27, 2014 at 10:28

unwind

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MONTYHS · Accepted Answer · 2014-02-27 10:26:51Z

 int row,col,i,j,tmp1,tmp2,tmp3,tmp4,tmp5,tmp6,tmp7;
  if(M==64&&N==64){
    for(row=0;row<N;row+=8){
        for(col=0;col<M;col+=8){
         for(j=0;j<2;j++){
            for(i=row;i<row+4;i++){
                tmp0=A[i+4*j][col+0];
                tmp1=A[i+4*j][col+1];
                tmp2=A[i+4*j][col+2];
                tmp3=A[i+4*j][col+3];
                tmp4=A[i+4*j][col+4];
                tmp5=A[i+4*j][col+5];
                tmp6=A[i+4*j][col+6];
                tmp7=A[i+4*j][col+7];

                B[col+0+4*j][i]=tmp0;
                B[col+1+4*j][i]=tmp1;
                B[col+2+4*j][i]=tmp2;
                B[col+3+4*j][i]=tmp3;
                B[col+0+4*j][i+4]=tmp4;
                B[col+1+4*j][i+4]=tmp5;
                B[col+2+4*j][i+4]=tmp6;
                B[col+3+4*j][i+4]=tmp7;

            }

Andy Stow Away · Accepted Answer · 2014-02-27 10:26:52Z

0

tmp0=A[i+4j][col+0];

It should be

tmp0=A[i+4*j][col+0];

replace at all places

answered Feb 27, 2014 at 10:26

Andy Stow Away

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Comments

Ashalynd · Accepted Answer · 2014-02-27 10:27:03Z

0

Multiplication should be called explicitly: in your case, 4*j instead of 4j.

answered Feb 27, 2014 at 10:27

Ashalynd

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