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But you’re describing indirection, not message passing. Is that the source of the confusion? Even C has indirection.

masklinn 5y ago
1. C does not have only indirection. 2. Message passing is an ideal, an ethos, the implementation (or the interface) can get in the way of that. That the messages are implemented as dynamically dispatched function calls… would be an implementation detail. Though with far ranging implications of course (especially in that the response is direct and synchronous rather than an other message as it would be in, say, Erlang). The mention of Self was not innocent, though it does use synchronously dynamic dispatch, a message might invoke a block, or just set or retrieve a value. If you’re asserting that it’s all « calling a function » then you’re basically just reductio at absurdum-ing everything to calling functions which… sure? You can model and reduce everything to lambda calculus.
- codeflo 5y ago
  > That the messages are implemented as dynamically dispatched function calls… would be an implementation detail. Though with far ranging implications of course It can't both be only an implementation detail and also have far reaching consequences. (It's not an implementation detail.) > You can model and reduce everything to lambda calculus. You actually can't, that's precisely my point. Lambda calculus is inherently "synchronous". You can't capture the full semantics of actual message passing with lambda calculus, you need a process calculus (like pi calculus) for that. (In case you're confused, this has nothing to do with Turing completeness, it's about modeling the behavior of concurrent systems. It's a really interesting subject.) The point is, lambda calculus is sufficient to model OOP method calls, including everything in Smalltalk and Self. It's not sufficient to model the semantics of Erlang messages.
- ProfHewitt 5y ago
  Concurrent computation is not reducible to the lambda calculus. See https://papers.ssrn.com/abstract=3603021 https://papers.ssrn.com/abstract=3603021

1. C does not have only indirection. 2. Message passing is an ideal, an ethos, the implementation (or the interface) can get in the way of that. That the messages are implemented as dynamically dispatched function calls… would be an implementation detail. Though with far ranging implications of course (especially in that the response is direct and synchronous rather than an other message as it would be in, say, Erlang). The mention of Self was not innocent, though it does use synchronously dynamic dispatch, a message might invoke a block, or just set or retrieve a value. If you’re asserting that it’s all « calling a function » then you’re basically just reductio at absurdum-ing everything to calling functions which… sure? You can model and reduce everything to lambda calculus.

codeflo 5y ago
> That the messages are implemented as dynamically dispatched function calls… would be an implementation detail. Though with far ranging implications of course It can't both be only an implementation detail and also have far reaching consequences. (It's not an implementation detail.) > You can model and reduce everything to lambda calculus. You actually can't, that's precisely my point. Lambda calculus is inherently "synchronous". You can't capture the full semantics of actual message passing with lambda calculus, you need a process calculus (like pi calculus) for that. (In case you're confused, this has nothing to do with Turing completeness, it's about modeling the behavior of concurrent systems. It's a really interesting subject.) The point is, lambda calculus is sufficient to model OOP method calls, including everything in Smalltalk and Self. It's not sufficient to model the semantics of Erlang messages.
ProfHewitt 5y ago
Concurrent computation is not reducible to the lambda calculus. See https://papers.ssrn.com/abstract=3603021 https://papers.ssrn.com/abstract=3603021