A killer feature of FORTRAN. C90 workarounds are terrible. Fortunately, C99 rescues us:

void vector_add(int n, int x[n], int a[n], int b[n]) {
  for(int i = 0; i < n; i++) x[i] = a[i] + b[i];
}

If the dimension of the vectors should be last:

void vector_add(int n; int x[n], int a[n], int b[n], int n) {
  for(int i = 0; i < n; i++) x[i] = a[i] + b[i];
}

This feature is also a GNU C extension.

The C99 committee listened to FORTRAN programmers and introduced <tgmath.h>, a type-generic edition of <math.h>. With this header, we no longer have to choose wisely from log, logf, logl, … We simply write log.

C99 introduced a complex data type. I wonder how it compares.

I hate this limitation of C. Luckily, most of the time it doesn’t bother me.

GNU C nested functions seem at least as powerful, though it is a shame there is no notation for anonymous functions. But yes, standard C is lacking here.

I’m jealous of this feature, though I can tolerate workarounds. Observe we need more than exp, expf, expl: we also require a routine tuned for the case when the base is a float and the exponent is an integer.

Workarounds in C are less pleasant but still tolerable.

Pointers can hamper compiler optimization, but they can also help. Hopefully, the restrict keyword of C99 will alleviate the thornier problems with explicit pointers.

Except for inner loops, the savings are slight. However, C programmers should be aware that some situations call for replacing dynamic allocation with static allocation.

The C99 restrict feature levels the playing field in theory, but FORTRAN might have the upper hand because all pointers are restricted by default, and FORTRAN programmers are more conscious of the difference between restricted and explicit pointers.

Another feature that was at last addressed with C99. Also, GNU C supports 80-bit and 128-bit floating point types.

This is indeed confusing for beginners. The size 1 array trick can take some of the pain away, but ultimately a C programmer must acquire familiarity with pointers and memory addresses.

I would have also mentioned x[]. This is perhaps even more perplexing, as its meaning is context-dependent. I wonder if this is necessary for maximum performance. Would C be less efficient with syntactic separation of arrays and pointers?

The documents lists other FORTRAN advantages, but I found these less compelling. In fact, some seem like FORTRAN disadvantages, as I appreciate case sensitivity, reserved words, recursion, and a smaller standard library.

I don’t understand why being able to pass all variables by reference is touted as a benefit. Why would it generate more efficient assembly than passing pointers around?