foo.c: In function ‘main’:
foo.c:7:11: warning: right-hand operand of comma expression has no effect [-Wunused-value]
    7 |    for(i=2,i<20,i++)
      |           ^
foo.c:7:20: error: expected ‘;’ before ‘)’ token
    7 |    for(i=2,i<20,i++)
      |                    ^
      |                    ;
foo.c:7:20: error: expected expression before ‘)’ token
foo.c:8:24: error: expected expression before ‘[’ token
    8 |            f[i]=f[i-1]+[i-2];
      |                        ^
foo.c:9:11: warning: right-hand operand of comma expression has no effect [-Wunused-value]
    9 |    for(i=0,i<20,i++)
      |           ^
foo.c:9:20: error: expected ‘;’ before ‘)’ token
    9 |    for(i=0,i<20,i++)
      |                    ^
      |                    ;
foo.c:9:20: error: expected expression before ‘)’ token