auto merge of #5213 : erickt/rust/vec-ref, r=graydon

This patch series changes a handful of vec functions to return references instead of copies. The one downside with making this change is that these functions aren't usable in a couple cases now due to some purity complaints. For example, this [change](erickt@c31e81a#L1R87). I couldn't figure out a way to get `last` to work on a `@mut ~[...]` type, so I ended up having to use `*crate_cache[crate_cache.len() - 1].metas`.

Author: bors

src/libcore/vec.rs

@@ -211,40 +211,41 @@ pub pure fn build_sized_opt<A>(size: Option<uint>,
 // Accessors
 
 /// Returns the first element of a vector
-pub pure fn head<T:Copy>(v: &[const T]) -> T { v[0] }
-
-/// Returns a vector containing all but the first element of a slice
-pub pure fn tail<T:Copy>(v: &[const T]) -> ~[T] {
-    slice(v, 1u, len(v)).to_vec()
+pub pure fn head<T>(v: &r/[T]) -> &r/T {
+    if v.len() == 0 { fail!(~"head: empty vector") }
+    &v[0]
 }
 
-/**
- * Returns a vector containing all but the first `n` \
- * elements of a slice
- */
-pub pure fn tailn<T:Copy>(v: &[const T], n: uint) -> ~[T] {
-    slice(v, n, len(v)).to_vec()
+/// Returns `Some(x)` where `x` is the first element of the slice `v`,
+/// or `None` if the vector is empty.
+pub pure fn head_opt<T>(v: &r/[T]) -> Option<&r/T> {
+    if v.len() == 0 { None } else { Some(&v[0]) }
 }
 
+/// Returns a vector containing all but the first element of a slice
+pub pure fn tail<T>(v: &r/[T]) -> &r/[T] { slice(v, 1, v.len()) }
+
+/// Returns a vector containing all but the first `n` elements of a slice
+pub pure fn tailn<T>(v: &r/[T], n: uint) -> &r/[T] { slice(v, n, v.len()) }
+
 /// Returns a vector containing all but the last element of a slice
-pub pure fn init<T:Copy>(v: &[const T]) -> ~[T] {
-    assert len(v) != 0u;
-    slice(v, 0u, len(v) - 1u).to_vec()
+pub pure fn init<T>(v: &r/[T]) -> &r/[T] { slice(v, 0, v.len() - 1) }
+
+/// Returns a vector containing all but the last `n' elements of a slice
+pub pure fn initn<T>(v: &r/[T], n: uint) -> &r/[T] {
+    slice(v, 0, v.len() - n)
 }
 
 /// Returns the last element of the slice `v`, failing if the slice is empty.
-pub pure fn last<T:Copy>(v: &[const T]) -> T {
-    if len(v) == 0u { fail!(~"last_unsafe: empty vector") }
-    v[len(v) - 1u]
+pub pure fn last<T>(v: &r/[T]) -> &r/T {
+    if v.len() == 0 { fail!(~"last: empty vector") }
+    &v[v.len() - 1]
 }
 
-/**
- * Returns `Some(x)` where `x` is the last element of the slice `v`,
- * or `none` if the vector is empty.
- */
-pub pure fn last_opt<T:Copy>(v: &[const T]) -> Option<T> {
-    if len(v) == 0u { return None; }
-    Some(v[len(v) - 1u])
+/// Returns `Some(x)` where `x` is the last element of the slice `v`, or
+/// `None` if the vector is empty.
+pub pure fn last_opt<T>(v: &r/[T]) -> Option<&r/T> {
+    if v.len() == 0 { None } else { Some(&v[v.len() - 1]) }
 }
 
 /// Return a slice that points into another slice.
@@ -1692,41 +1693,29 @@ impl<T> Container for &[const T] {
 }
 
 pub trait CopyableVector<T> {
-    pure fn head(&self) -> T;
-    pure fn init(&self) -> ~[T];
-    pure fn last(&self) -> T;
     pure fn slice(&self, start: uint, end: uint) -> ~[T];
-    pure fn tail(&self) -> ~[T];
 }
 
 /// Extension methods for vectors
-impl<T:Copy> CopyableVector<T> for &[const T] {
-    /// Returns the first element of a vector
-    #[inline]
-    pure fn head(&self) -> T { head(*self) }
-
-    /// Returns all but the last elemnt of a vector
-    #[inline]
-    pure fn init(&self) -> ~[T] { init(*self) }
-
-    /// Returns the last element of a `v`, failing if the vector is empty.
-    #[inline]
-    pure fn last(&self) -> T { last(*self) }
-
+impl<T: Copy> CopyableVector<T> for &[const T] {
     /// Returns a copy of the elements from [`start`..`end`) from `v`.
     #[inline]
     pure fn slice(&self, start: uint, end: uint) -> ~[T] {
         slice(*self, start, end).to_vec()
     }
-
-    /// Returns all but the first element of a vector
-    #[inline]
-    pure fn tail(&self) -> ~[T] { tail(*self) }
 }
 
 pub trait ImmutableVector<T> {
     pure fn view(&self, start: uint, end: uint) -> &self/[T];
-    pure fn foldr<U:Copy>(&self, z: U, p: fn(t: &T, u: U) -> U) -> U;
+    pure fn head(&self) -> &self/T;
+    pure fn head_opt(&self) -> Option<&self/T>;
+    pure fn tail(&self) -> &self/[T];
+    pure fn tailn(&self, n: uint) -> &self/[T];
+    pure fn init(&self) -> &self/[T];
+    pure fn initn(&self, n: uint) -> &self/[T];
+    pure fn last(&self) -> &self/T;
+    pure fn last_opt(&self) -> Option<&self/T>;
+    pure fn foldr<U: Copy>(&self, z: U, p: fn(t: &T, u: U) -> U) -> U;
     pure fn map<U>(&self, f: fn(t: &T) -> U) -> ~[U];
     pure fn mapi<U>(&self, f: fn(uint, t: &T) -> U) -> ~[U];
     fn map_r<U>(&self, f: fn(x: &T) -> U) -> ~[U];
@@ -1743,6 +1732,38 @@ impl<T> ImmutableVector<T> for &[T] {
         slice(*self, start, end)
     }
 
+    /// Returns the first element of a vector, failing if the vector is empty.
+    #[inline]
+    pure fn head(&self) -> &self/T { head(*self) }
+
+    /// Returns the first element of a vector
+    #[inline]
+    pure fn head_opt(&self) -> Option<&self/T> { head_opt(*self) }
+
+    /// Returns all but the first element of a vector
+    #[inline]
+    pure fn tail(&self) -> &self/[T] { tail(*self) }
+
+    /// Returns all but the first `n' elements of a vector
+    #[inline]
+    pure fn tailn(&self, n: uint) -> &self/[T] { tailn(*self, n) }
+
+    /// Returns all but the last elemnt of a vector
+    #[inline]
+    pure fn init(&self) -> &self/[T] { init(*self) }
+
+    /// Returns all but the last `n' elemnts of a vector
+    #[inline]
+    pure fn initn(&self, n: uint) -> &self/[T] { initn(*self, n) }
+
+    /// Returns the last element of a `v`, failing if the vector is empty.
+    #[inline]
+    pure fn last(&self) -> &self/T { last(*self) }
+
+    /// Returns the last element of a `v`, failing if the vector is empty.
+    #[inline]
+    pure fn last_opt(&self) -> Option<&self/T> { last_opt(*self) }
+
     /// Reduce a vector from right to left
     #[inline]
     pure fn foldr<U:Copy>(&self, z: U, p: fn(t: &T, u: U) -> U) -> U {
@@ -2570,27 +2591,117 @@ mod tests {
 
     #[test]
     fn test_head() {
-        let a = ~[11, 12];
-        assert (head(a) == 11);
+        let mut a = ~[11];
+        assert a.head() == &11;
+        a = ~[11, 12];
+        assert a.head() == &11;
+    }
+
+    #[test]
+    #[should_fail]
+    #[ignore(cfg(windows))]
+    fn test_head_empty() {
+        let a: ~[int] = ~[];
+        a.head();
+    }
+
+    #[test]
+    fn test_head_opt() {
+        let mut a = ~[];
+        assert a.head_opt() == None;
+        a = ~[11];
+        assert a.head_opt().unwrap() == &11;
+        a = ~[11, 12];
+        assert a.head_opt().unwrap() == &11;
     }
 
     #[test]
     fn test_tail() {
         let mut a = ~[11];
-        assert (tail(a) == ~[]);
+        assert a.tail() == &[];
+        a = ~[11, 12];
+        assert a.tail() == &[12];
+    }
+
+    #[test]
+    #[should_fail]
+    #[ignore(cfg(windows))]
+    fn test_tail_empty() {
+        let a: ~[int] = ~[];
+        a.tail();
+    }
 
+    #[test]
+    fn test_tailn() {
+        let mut a = ~[11, 12, 13];
+        assert a.tailn(0) == &[11, 12, 13];
+        a = ~[11, 12, 13];
+        assert a.tailn(2) == &[13];
+    }
+
+    #[test]
+    #[should_fail]
+    #[ignore(cfg(windows))]
+    fn test_tailn_empty() {
+        let a: ~[int] = ~[];
+        a.tailn(2);
+    }
+
+    #[test]
+    fn test_init() {
+        let mut a = ~[11];
+        assert a.init() == &[];
         a = ~[11, 12];
-        assert (tail(a) == ~[12]);
+        assert a.init() == &[11];
+    }
+
+    #[init]
+    #[should_fail]
+    #[ignore(cfg(windows))]
+    fn test_init_empty() {
+        let a: ~[int] = ~[];
+        a.init();
+    }
+
+    #[test]
+    fn test_initn() {
+        let mut a = ~[11, 12, 13];
+        assert a.initn(0) == &[11, 12, 13];
+        a = ~[11, 12, 13];
+        assert a.initn(2) == &[11];
+    }
+
+    #[init]
+    #[should_fail]
+    #[ignore(cfg(windows))]
+    fn test_initn_empty() {
+        let a: ~[int] = ~[];
+        a.initn(2);
     }
 
     #[test]
     fn test_last() {
-        let mut n = last_opt(~[]);
-        assert (n.is_none());
-        n = last_opt(~[1, 2, 3]);
-        assert (n == Some(3));
-        n = last_opt(~[1, 2, 3, 4, 5]);
-        assert (n == Some(5));
+        let mut a = ~[11];
+        assert a.last() == &11;
+        a = ~[11, 12];
+        assert a.last() == &12;
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_last_empty() {
+        let a: ~[int] = ~[];
+        a.last();
+    }
+
+    #[test]
+    fn test_last_opt() {
+        let mut a = ~[];
+        assert a.last_opt() == None;
+        a = ~[11];
+        assert a.last_opt().unwrap() == &11;
+        a = ~[11, 12];
+        assert a.last_opt().unwrap() == &12;
     }
 
     #[test]
@@ -3262,12 +3373,6 @@ mod tests {
         assert (v2[1] == 10);
     }
 
-    #[test]
-    fn test_init() {
-        let v = init(~[1, 2, 3]);
-        assert v == ~[1, 2];
-    }
-
     #[test]
     fn test_split() {
         fn f(x: &int) -> bool { *x == 3 }
@@ -3332,13 +3437,6 @@ mod tests {
                (~[], ~[1, 2, 3]);
     }
 
-    #[test]
-    #[should_fail]
-    #[ignore(cfg(windows))]
-    fn test_init_empty() {
-        init::<int>(~[]);
-    }
-
     #[test]
     fn test_concat() {
         assert concat(~[~[1], ~[2,3]]) == ~[1, 2, 3];

src/librust/rust.rc

@@ -130,7 +130,7 @@ fn cmd_help(args: &[~str]) -> ValidUsage {
                     UsgExec(commandline) => {
                         let words = str::words(commandline);
                         let (prog, args) = (words.head(), words.tail());
-                        run::run_program(prog, args);
+                        run::run_program(*prog, args);
                     }
                 }
                 Valid
@@ -186,7 +186,10 @@ fn do_command(command: &Command, args: &[~str]) -> ValidUsage {
         Exec(commandline) => {
             let words = str::words(commandline);
             let (prog, prog_args) = (words.head(), words.tail());
-            let exitstatus = run::run_program(prog, prog_args + args);
+            let exitstatus = run::run_program(
+                *prog,
+                vec::append(vec::from_slice(prog_args), args)
+            );
             os::set_exit_status(exitstatus);
             Valid
         }
@@ -221,11 +224,12 @@ fn usage() {
 }
 
 pub fn main() {
-    let args = os::args().tail();
+    let os_args = os::args();
+    let args = os_args.tail();
 
     if !args.is_empty() {
         for commands.each |command| {
-            if command.cmd == args.head() {
+            if command.cmd == *args.head() {
                 let result = do_command(command, args.tail());
                 if result.is_valid() { return; }
             }

src/librustc/metadata/creader.rs

@@ -65,7 +65,7 @@ struct cache_entry {
     metas: @~[@ast::meta_item]
 }
 
-fn dump_crates(+crate_cache: @mut ~[cache_entry]) {
+fn dump_crates(crate_cache: @mut ~[cache_entry]) {
     debug!("resolved crates:");
     for crate_cache.each |entry| {
         debug!("cnum: %?", entry.cnum);
@@ -81,7 +81,9 @@ fn warn_if_multiple_versions(e: @mut Env,
 
     if crate_cache.len() != 0u {
         let name = loader::crate_name_from_metas(
-            /*bad*/copy *crate_cache.last().metas);
+            *crate_cache[crate_cache.len() - 1].metas
+        );
+
         let (matches, non_matches) =
             partition(crate_cache.map_to_vec(|&entry| {
                 let othername = loader::crate_name_from_metas(

src/librustc/metadata/decoder.rs

@@ -558,16 +558,18 @@ pub fn maybe_get_item_ast(intr: @ident_interner, cdata: cmd, tcx: ty::ctxt,
                        -> csearch::found_ast {
     debug!("Looking up item: %d", id);
     let item_doc = lookup_item(id, cdata.data);
-    let path = vec::init(item_path(intr, item_doc));
+    let path = {
+        let item_path = item_path(intr, item_doc);
+        vec::from_slice(item_path.init())
+    };
     match decode_inlined_item(cdata, tcx, path, item_doc) {
       Some(ref ii) => csearch::found((/*bad*/copy *ii)),
       None => {
         match item_parent_item(item_doc) {
           Some(did) => {
             let did = translate_def_id(cdata, did);
             let parent_item = lookup_item(did.node, cdata.data);
-            match decode_inlined_item(cdata, tcx, path,
-                                               parent_item) {
+            match decode_inlined_item(cdata, tcx, path, parent_item) {
               Some(ref ii) => csearch::found_parent(did, (/*bad*/copy *ii)),
               None => csearch::not_found
             }