Thanks David,
> It looks like this might be a useful reference:
>
> R. J. Popplestone: The Design Philosophy of POP-2. in: D. Michie:
> Machine Intelligence 3, Edinburgh at the University Press, 1968
>
> but unfortunately I can't find the text online. It's cited in this
> Wikipedia page:
>
> https://en.wikipedia.org/wiki/First-class_citizen
>
> which contains this excerpt:
>
> * All items can be the actual parameters of functions
> * All items can be returned as results of functions
> * All items can be the subject of assignment statements
> * All items can be tested for equality.
I've added this to
https://www.cs.bham.ac.uk/research/projects/poplog/V16/AREADME.html#Popplestone
I've also failed to find an online version of the article. From this website
https://www.doc.ic.ac.uk/~shm/MI/mi.html
it appears that none of the early volumes in the Machine Intelligence
series have been made available online. It's a pity: having them available
could help to educate people mesmerised by the (partial) successes of Deep
Learning.
Aaron
