a more recent set of slides on the relation between abc and python is https://www.cwi.nl/documents/195216/Meertens-20191121.pdf which describes again how abc was started in 01975. this helpfully clarifies the timeline: b0 was 01975; b1 was 01978; b2 was 01979; and b∞ = abc was 01985. so specifically the point at which setl inspired the replacement of conventional arrays in b1 with associative arrays in b2 was 01979, which was the year 7th edition unix was released and the aho, weinberger, and kernighan paper was published in sp&e

a question of some interest to me here is what platform they were developing abc on in 01979. clearly it couldn't have been the ibm pc, which wouldn't come out until 01983 (and as far as i know abc on the ibm pc only runs under cygwin or 32-bit microsoft windows), or macos (which came out in 01984) or atari tos, which wouldn't come out until 01985. and so far i haven't seen any mention in the history of abc of other operating systems of the time like cp/m, vm/cms, dg rdos, tenex, or tops-20. the most likely platform would seem to have been unix, on which awk was one of the relatively few programming languages available. perhaps at some point i'll run across an answer to that question in the abc papers

python adopted awk's syntax for putting 10 into roman['x'], which was `put 10 in roman['x']` in abc, but `roman['x'] = 10` in awk and python. abc's syntax is uppercase, presumably case-insensitive, separates words with apostrophes, and departs widely from conventional infix syntax. python's syntax is case-sensitive, mostly lowercase, and conventionally infix, features that have become common through the influence of unix. python's control structures are for, while, and if/elif/else, as in algol and in abc, and indentation-sensitive as in abc, but uses a conventional ascii syntax rather than abc's scratch-like syntax-directed editor

abc was statically typed with a hindley-milner type system ('the type system is similar to that of lcf', p. 15 (18/91) of the draft proposal), while python is dynamically typed, like smalltalk, lisp, and awk

if meertens got his daring notion of storing everything in associative arrays from awk, he certainly doesn't mention it. instead he mentions setl a lot! the draft proposal doesn't cite awk but it also doesn't cite setl; it cites the algol-68 report, milner's lcf typing paper, a cleaveland and uzgalis paper about grammars, gehani, and three of his own papers, from 01976, 01978, and 01981. unfortunately i can't find any of those earlier meertens papers online

the wikipedia page about setl says

> SETL provides two basic aggregate data types: (unordered) sets, and tuples.[1][2][5] The elements of sets and tuples can be of any arbitrary type, including sets and tuples themselves, except the undefined value om[1] (sometimes capitalized: OM).[6] Maps are provided as sets of pairs (i.e., tuples of length 2) and can have arbitrary domain and range types.[1][5]

but it's citing papers about setl from 01985 there, well after awk had supposedly popularized the notion of associative arrays

however, in meertens's essay on python's history, he cites a 01975 paper on setl! https://www.softwarepreservation.org/projects/SETL/setl/doc/...

> Jacob T. Schwartz. ON PROGRAMMING: An Interim Report on the SETL Project. Part I: Generalities; Part II: The SETL Language and Examples of Its Use. Computer Science Department, Courant Institute of Mathematical Sciences, New York University, revised June 1975.

this discusses how setl represented data in memory starting on p. 57 (57/689). it used hash tables to represent sets, including sets of tuples, rather than the ill-advised balanced-tree approach used by abc. (python, like awk and setl, uses hash tables.) on pp. 62–63 (62–63/689) it explains:

> The hash code of a tuple is taken to be the hash code of
its first component, for reasons that will become clear in the
next section. The hash code of a set is the exclusive or of
the hash codes of all its members. (...)

> — Tuples in Sets —

> Though expressible in terms of the membership test, "with", and
"less" operations, functional evaluation plays so important a role
in SETL algorithms that we treat it as a primitive.

> SETL makes three types of set-related functional evaluation
operators available:

> - f(x)

> - f{x}

> - f[s]

> The most fundamental of these is f{x}, which invokes a search
over f for all n-tuples that begin with x (n ≥ 2), and which
yields as result the set of all tails of these n-tuples. More
precisely, in SETL:

> f{x} = if #y eq 2 then y(2) else tℓ y, y ∈ f | type y eq tupl and #y ge 2 and hd y eq x}

> The operation f(x) has a similar definition but includes a single valuedness check:

> f(x) = if #f{x} eq 1 then ∋f{x} else Ω

> The operation f[s] is adequately defined in terms of f{x}:

> f[s] = [+: x ∈ s] f{x}

i am fairly confident that the f{x} definition translates into current vernacular python as the set-comprehension {y[2] if len(y) == 2 else y[1:] for y in f if type(y) == tuple and len(y) >= 2 and y[0] == x}.

so, it becomes clear that already in 01975 setl treated sets of tuples as maps, which is to say associative arrays, but it didn't use the 'associative array' terminology used by meertens in 01981, or for that matter 'maps'. to look up an element in the map, it didn't use the f[x] notation used by python, awk, and abc; instead it used f(x). further explanation on pp. 64–65 (64–65/689) clarifies that really it is more accurate to think of 'sets of tuples' as trees; each item in the tuple entails following an additional level of pointers to a further hash table

(in a number of other notational details, python and presumably abc follows setl: start: or start:end for array index ranges, + for string concatenation, * for string repetition, boolean operators spelled out as and, or, and not. but indexing maps is far from the only difference)

abc (including b as described in the 01981 report) also seems to lack the f{x} operation and its possibility of associating an arbitrary-sized set of values with each key. this is a nontrivial semantic divergence

so if abc got its idea of tables from setl, but used awk's terminology, notation, and semantics for them (and its own ill-conceived balanced-tree implementation, used by neither), and decided to adopt the table idea in the year when awk was released, probably on the platform that awk was released on, i think it's reasonable to assign some share of the credit for abc's tables to awk? even if not all of it

but if that's so, then why didn't meertens credit aho, weinberger, and kernighan? i don't know. maybe awk's loosey-goosey nature was repugnant to him. maybe weinberger is jewish and meertens is secretely anti-semitic. maybe meertens thought that awk's loosey-goosey nature would be repugnant to the dijkstra-honoring dutch computer science establishment. maybe aho insulted meertens's favorite beer one time when he visited the netherlands. or maybe he thought it would be unfair for aho, weinberger, and kernighan to steal the thunder of schwartz, who did after all precede them in developing a general-purpose language whose memory was based entirely on hash tables. from a certain point of view that would be like crediting carl sagan with the theory of relativity because he explained it on nova