CLU had for loops with iterators (generators) and yield in the mid–late 1970s [0]. The Icon programming language around the same time had similar generator features [1] (with yield spelled “suspend”). Ada (1983) also had such features I believe. These weren’t completely unknown language features.

[0] https://publications.csail.mit.edu/lcs/pubs/pdf/MIT-LCS-TR-2...

[1] https://dl.acm.org/doi/pdf/10.1145/800055.802034

Ada didn’t have generators back then and still doesn’t ( I think its being considered for inclusion soon ). But it had all the other features.

A task type with an entry is effectively a generator.

Bitsavers has a copy of the HC 1.2 reference manual (1985)

It describes underscores in numbers, case ranges, named parameters, nested functions, and full function variables.

    https://bitsavers.org/pdf/metaware/High_C_Language_Reference_Manual_1.2_Nov85.pdf

See Appendix A - 50 odd pages from the end of the file.

Metaware was a prolific compiler company based out of Santa Cruz in the 80s/90s. Loved what they did, they also had a very interesting culture. I knew about them through cough shady cough sites when learning and writing code back in the day.

Not really, if you dig into archives of high level programming languages since FORTRAN, Lisp, ALGOL and COBOL sprung into existence, you will see lots of these language ideas.

You will also discover the rich history of systems programming languages, and how similar C and Go design's are in ignoring what was being done in other ecosystems, and past experiences.

Yeah, it's sad to see those features as novel features instead of part of the standard list of features most programming languages supply.

There's a link to the compiler manuals at https://winworldpc.com/product/metaware-high-c-cpp/33x

The C manual PDF file mentions a 2007 copyright.