Comment by dfawcus

The other example of nested functions which you've not mentioned was in Metaware High C.

There they allowed nested functions, but also what they termed "full function values", being a form of fat pointer. Certainly I came across it in High-C v1.7 in 1990, and the full manual for an earlier version (1.2?) from around '85 can be found on Bitsavers.

It had a syntax like:

    extern void Quick_sort(
      int Lo, int Hi, int Compare(int a, int b)!,
      void Swap(int a,int b)!
    );

    static Sort_private_table() {
      Entry Entries[100];
      int Compare(int a,int b) {
        return Entries[a] < Entries[b];
      }
      void Swap(int a,int b) {
        Entry Temp = Entries[a];
        Entries[a] = Entries[b];
        Entries[b] = Temp;
      }
      ...
      Quick_sort(1,100,Compare,Swap);
    }

The above is an extract from their language reference, which you can find here:

https://archive.org/download/Yoshizuki_UnRenamed_Files__D-V/...