From 5f5a1127865f96f04fc4be82c2940f1c532e7aac Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Tue, 14 May 2019 17:18:04 +0100
Subject: [PATCH] wip

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+
+In many respects Rust is a competent but not particularly novel
+language.
+
+Powerful.
+
+Reference to Blub languages.
+
+B======================================================================B
+
+[ MM survey slide ]
+
+Firstly, I'm going to go into some detail about Rust's one very novel
+property: it's approach to memory management.  Let us consider,
+particularly, dynamically allocated memory.
+
+Until now there have been basically two approaches:
+
+In lower-level languages like C, C++ and assembler, you as the
+programmer must know whenever memory allocation is occurring, and
+control when that memory is freed, usually with explicit code.
+Mistakes lead to bugs - often, bugs which are very hard to track down.
+There are some static checkers, and coding conventions, which help to
+reduce the number of these bugs but they are still a big problem even
+with the most careful software development practices.
+
+In higher-level languages, memory allocation is often implicit and
+deallocation is handled automatically by a garbage collector.  This is
+convenient for the programmer.  But it requires support from a
+language runtime, which is awkward in some environments and makes it
+hard to interface to other languages.  And it costs performance -
+sometimes, a lot of performance.  Traditionally, garbage-collected
+languages have focused on programmer convenience, or programming
+language power, rather than performance.
+
+[ MM survey slide + Rust ]
+
+Rust has a different approach.  Each object in a Rust program has
+exactly one owner; for a local variable that owner is the variable.
+For an object in a complex data structure, the data structure is the
+owner (and of course that data structure has, in turn, an owner).  In
+many ways this resembles informal notions of object ownership which
+programmers have typically used in C and C++ to make their code
+comprehensible.
+
+But in Rust the ownership is known to the language, and the rules
+surrounding ownership are enforced by the compiler.  When an object
+ceases to have an owner, it is freed.
+
+This ownership system is used not only for dynamically allocated
+objects, but for local variables, and statically allocated objects.
+
+[ Borrowing example slide ]  https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html#mutable-references
+
+To allow an object to be accessed other than through owner, Rust
+formalises the notion of borrowing.  An object can be borrowed by
+writing the ampersand, giving a reference.  The compiler checks that
+the object will outlive the reference.
+
+[ dangling reference error example  https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html#dangling-references ]
+
+Borrows (that is, references) come in two kinds: mutable and
+immutable.  You can have many immutable references at once.  A mutable
+reference permits modification, and provides exclusive access.
+
+[ Borrowing example slide ]  https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html#mutable-references
+
+That's what the `mut' is doing in that example.
+
+
+
+
+You can lend Objects which 
+
+
+This ownership is
+known to the 
+
+
+tends to lead to 
+
+
+
+write explicit code allocate memory, and and free allre
-- 
2.30.2