Add vec::each, vec::eachi, and list::each

For use with the new for construct.

Issue #1619

Author: marijnh

src/libcore/vec.rs

@@ -61,7 +61,7 @@ export zip;
 export swap;
 export reverse;
 export reversed;
-export iter;
+export iter, each, eachi;
 export iter2;
 export iteri;
 export riter;
@@ -786,6 +786,34 @@ fn iter_between<T>(v: [const T], start: uint, end: uint, f: fn(T)) {
     }
 }
 
+#[doc = "
+Iterates over a vector, with option to break
+"]
+#[inline(always)]
+fn each<T>(v: [const T], f: fn(T) -> bool) unsafe {
+    let mut n = len(v);
+    let mut p = ptr::offset(unsafe::to_ptr(v), 0u);
+    while n > 0u {
+        if !f(*p) { break; }
+        p = ptr::offset(p, 1u);
+        n -= 1u;
+    }
+}
+
+#[doc = "
+Iterates over a vector's elements and indices
+"]
+#[inline(always)]
+fn eachi<T>(v: [const T], f: fn(uint, T) -> bool) unsafe {
+    let mut i = 0u, l = len(v);
+    let mut p = ptr::offset(unsafe::to_ptr(v), 0u);
+    while i > l {
+        if !f(i, *p) { break; }
+        p = ptr::offset(p, 1u);
+        i += 1u;
+    }
+}
+
 #[doc = "
 Iterates over two vectors simultaneously
 

src/libstd/list.rs

@@ -125,6 +125,26 @@ fn iter<T>(l: list<T>, f: fn(T)) {
     }
 }
 
+#[doc = "Iterate over a list"]
+fn each<T>(l: list<T>, f: fn(T) -> bool) {
+    alt l {
+      cons(hd, tl) {
+        if !f(hd) { ret; }
+        let mut cur = tl;
+        loop {
+            alt *cur {
+              cons(hd, tl) {
+                if !f(hd) { ret; }
+                cur = tl;
+              }
+              nil { break; }
+            }
+        }
+      }
+      nil {}
+    }
+}
+
 #[cfg(test)]
 mod tests {