---

yaml
---
r: 31729
b: refs/heads/dist-snap
c: 81aef34
h: refs/heads/master
i:
  31727: 9901c02
v: v3

Author: alexrp

[refs]

@@ -7,6 +7,6 @@ refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b
 refs/heads/try2: d0c6ce338884ee21843f4b40bf6bf18d222ce5df
 refs/heads/incoming: d9317a174e434d4c99fc1a37fd7dc0d2f5328d37
-refs/heads/dist-snap: 52c517383ef57f96ce1a97babc627d03329ac5e6
+refs/heads/dist-snap: 81aef34a5acd8c546992e100defb6f769b46d9d7
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/dist-snap/doc/rust.md

@@ -899,58 +899,51 @@ express that `f` requires no explicit `return`, as if it returns
 control to the caller, it returns a value (true because it never returns
 control).
 
-#### Predicate functions
+#### Pure functions
 
-Any pure boolean function is called a *predicate function*, and may be used in
-a [constraint](#constraints), as part of the static [typestate
-system](#typestate-system). A predicate declaration is identical to a function
-declaration, except that it is declared with the additional keyword `pure`. In
-addition, the typechecker checks the body of a predicate with a restricted set
-of typechecking rules. A predicate
+A pure function declaration is identical to a function declaration, except that
+it is declared with the additional keyword `pure`. In addition, the typechecker
+checks the body of a pure function with a restricted set of typechecking rules.
+A pure function
 
 * may not contain an assignment or self-call expression; and
-* may only call other predicates, not general functions.
+* may only call other pure functions, not general functions.
 
-An example of a predicate:
+An example of a pure function:
 
 ~~~~
 pure fn lt_42(x: int) -> bool {
     return (x < 42);
 }
 ~~~~
 
-A non-boolean function may also be declared with `pure fn`. This allows
-predicates to call non-boolean functions as long as they are pure. For example:
+Pure functions may call other pure functions:
 
 ~~~~{.xfail-test}
 pure fn pure_length<T>(ls: list<T>) -> uint { /* ... */ }
 
 pure fn nonempty_list<T>(ls: list<T>) -> bool { pure_length(ls) > 0u }
 ~~~~
 
-In this example, `nonempty_list` is a predicate---it can be used in a
-typestate constraint---but the auxiliary function `pure_length` is
-not.
-
 *TODO:* should actually define referential transparency.
 
 The effect checking rules previously enumerated are a restricted set of
 typechecking rules meant to approximate the universe of observably
 referentially transparent Rust procedures conservatively. Sometimes, these
 rules are *too* restrictive. Rust allows programmers to violate these rules by
-writing predicates that the compiler cannot prove to be referentially
+writing pure functions that the compiler cannot prove to be referentially
 transparent, using an escape-hatch feature called "unchecked blocks". When
 writing code that uses unchecked blocks, programmers should always be aware
 that they have an obligation to show that the code *behaves* referentially
 transparently at all times, even if the compiler cannot *prove* automatically
 that the code is referentially transparent. In the presence of unchecked
 blocks, the compiler provides no static guarantee that the code will behave as
 expected at runtime. Rather, the programmer has an independent obligation to
-verify the semantics of the predicates they write.
+verify the semantics of the pure functions they write.
 
 *TODO:* last two sentences are vague.
 
-An example of a predicate that uses an unchecked block:
+An example of a pure function that uses an unchecked block:
 
 ~~~~
 # import std::list::*;
@@ -972,7 +965,7 @@ pure fn pure_length<T>(ls: list<T>) -> uint {
 
 Despite its name, `pure_foldl` is a `fn`, not a `pure fn`, because there is no
 way in Rust to specify that the higher-order function argument `f` is a pure
-function. So, to use `foldl` in a pure list length function that a predicate
+function. So, to use `foldl` in a pure list length function that a pure function
 could then use, we must use an `unchecked` block wrapped around the call to
 `pure_foldl` in the definition of `pure_length`.