diff --git a/src/comp/front/ext.rs b/src/comp/front/ext.rs
index d300febbc45b..34b60d4668f6 100644
--- a/src/comp/front/ext.rs
+++ b/src/comp/front/ext.rs
@@ -1,4 +1,4 @@
-
+import std::vec;
 import std::option;
 import std::map::hashmap;
 import driver::session::session;
@@ -6,20 +6,24 @@ import front::parser::parser;
 import util::common::span;
 import util::common::new_str_hash;
 
-type syntax_expander =
-    fn(&ext_ctxt, span, &vec[@ast::expr], option::t[str]) -> @ast::expr ;
-
-
-// Temporary: to introduce a tag in order to make a recursive type work
-tag syntax_extension { x(syntax_expander); }
+type syntax_expander = 
+    fn(&ext_ctxt, span, &vec[@ast::expr], option::t[str]) -> @ast::expr;
+type macro_definer = fn(&ext_ctxt, span, &vec[@ast::expr],
+                        option::t[str]) -> tup(str, syntax_extension);
 
+tag syntax_extension {
+    normal(syntax_expander);
+    macro_defining(macro_definer);
+}
 
 // A temporary hard-coded map of methods for expanding syntax extension
 // AST nodes into full ASTs
 fn syntax_expander_table() -> hashmap[str, syntax_extension] {
     auto syntax_expanders = new_str_hash[syntax_extension]();
-    syntax_expanders.insert("fmt", x(extfmt::expand_syntax_ext));
-    syntax_expanders.insert("env", x(extenv::expand_syntax_ext));
+    syntax_expanders.insert("fmt", normal(extfmt::expand_syntax_ext));
+    syntax_expanders.insert("env", normal(extenv::expand_syntax_ext));
+    syntax_expanders.insert("simplext",    
+                            macro_defining(extsimplext::add_new_extension));
     ret syntax_expanders;
 }
 
@@ -51,6 +55,37 @@ fn mk_ctxt(parser parser) -> ext_ctxt {
             span_unimpl=ext_span_unimpl,
             next_id=ext_next_id);
 }
+
+fn expr_to_str(&ext_ctxt cx, @ast::expr expr, str error) -> str {
+    alt (expr.node) {
+        case (ast::expr_lit(?l)) {
+            alt (l.node) {
+                case (ast::lit_str(?s, _)) { ret s; }
+                case (_) { cx.span_fatal(l.span, error); }
+            }
+        }
+        case (_) { cx.span_fatal(expr.span, error); }
+    }
+}
+
+fn expr_to_ident(&ext_ctxt cx, @ast::expr expr, str error) -> ast::ident {
+    alt(expr.node) {
+        case (ast::expr_path(?p)) {
+            if (vec::len(p.node.types) > 0u 
+                || vec::len(p.node.idents) != 1u) {
+                cx.span_fatal(expr.span, error);
+            } else {
+                ret p.node.idents.(0);
+            }
+        }
+        case (_) {
+            cx.span_fatal(expr.span, error);
+        }
+    }
+}
+
+
+
 //
 // Local Variables:
 // mode: rust
diff --git a/src/comp/front/extenv.rs b/src/comp/front/extenv.rs
index 1b1e0420e100..acfb93e1cdce 100644
--- a/src/comp/front/extenv.rs
+++ b/src/comp/front/extenv.rs
@@ -21,27 +21,13 @@ fn expand_syntax_ext(&ext_ctxt cx, common::span sp, &vec[@ast::expr] args,
     // FIXME: if this was more thorough it would manufacture an
     // option::t[str] rather than just an maybe-empty string.
 
-    auto var = expr_to_str(cx, args.(0));
+    auto var = expr_to_str(cx, args.(0), "#env requires a string");
     alt (generic_os::getenv(var)) {
         case (option::none) { ret make_new_str(cx, sp, ""); }
         case (option::some(?s)) { ret make_new_str(cx, sp, s); }
     }
 }
 
-
-// FIXME: duplicate code copied from extfmt:
-fn expr_to_str(&ext_ctxt cx, @ast::expr expr) -> str {
-    alt (expr.node) {
-        case (ast::expr_lit(?l)) {
-            alt (l.node) {
-                case (ast::lit_str(?s, _)) { ret s; }
-                case (_) { cx.span_fatal(l.span, "malformed #env call"); }
-            }
-        }
-        case (_) { cx.span_fatal(expr.span, "malformed #env call"); }
-    }
-}
-
 fn make_new_lit(&ext_ctxt cx, common::span sp, ast::lit_ lit) -> @ast::expr {
     auto sp_lit = @rec(node=lit, span=sp);
     ret @rec(id=cx.next_id(), node=ast::expr_lit(sp_lit), span=sp);
diff --git a/src/comp/front/extfmt.rs b/src/comp/front/extfmt.rs
index f68c36974c36..0696e0d2c697 100644
--- a/src/comp/front/extfmt.rs
+++ b/src/comp/front/extfmt.rs
@@ -20,7 +20,8 @@ fn expand_syntax_ext(&ext_ctxt cx, common::span sp, &vec[@ast::expr] args,
     if (vec::len[@ast::expr](args) == 0u) {
         cx.span_fatal(sp, "#fmt requires a format string");
     }
-    auto fmt = expr_to_str(cx, args.(0));
+    auto fmt = expr_to_str(cx, args.(0), "first argument to #fmt must be a "
+                           + "string literal.");
     auto fmtspan = args.(0).span;
     log "Format string:";
     log fmt;
@@ -32,20 +33,6 @@ fn expand_syntax_ext(&ext_ctxt cx, common::span sp, &vec[@ast::expr] args,
     ret pieces_to_expr(cx, sp, pieces, args);
 }
 
-fn expr_to_str(&ext_ctxt cx, @ast::expr expr) -> str {
-    auto err_msg = "first argument to #fmt must be a string literal";
-    alt (expr.node) {
-        case (ast::expr_lit(?l)) {
-            alt (l.node) {
-                case (ast::lit_str(?s, _)) { ret s; }
-                case (_) { cx.span_fatal(l.span, err_msg); }
-            }
-        }
-        case (_) { cx.span_fatal(expr.span, err_msg); }
-    }
-}
-
-
 // FIXME: A lot of these functions for producing expressions can probably
 // be factored out in common with other code that builds expressions.
 // FIXME: Cleanup the naming of these functions
diff --git a/src/comp/front/extsimplext.rs b/src/comp/front/extsimplext.rs
new file mode 100644
index 000000000000..3de737f0d53f
--- /dev/null
+++ b/src/comp/front/extsimplext.rs
@@ -0,0 +1,144 @@
+use std;
+
+import util::common::span;
+import std::vec;
+import std::option;
+import vec::map;
+import vec::len;
+import option::some;
+import option::none;
+
+import ext::syntax_extension;
+import ext::ext_ctxt;
+import ext::normal;
+import ext::expr_to_str;
+import ext::expr_to_ident;
+
+import fold::*;
+import ast::ident;
+import ast::path_;
+import ast::expr_path;
+
+export add_new_extension;
+
+
+//temporary, until 'position' shows up in the snapshot
+fn position[T](&T x, &vec[T] v) -> option::t[uint] {
+    let uint i = 0u;
+    while (i < len(v)) {
+        if (x == v.(i)) { ret some[uint](i); }
+        i += 1u;
+    }
+    ret none[uint];
+}
+
+// substitute, in a position that's required to be an ident
+fn subst_ident(&ext_ctxt cx, &vec[@ast::expr] args, 
+               @vec[ident] param_names, &ident i, ast_fold fld) -> ident {
+    alt (position(i, *param_names)) {
+        case (some[uint](?idx)) {
+            ret expr_to_ident(cx, args.(idx), 
+                              "This argument is expanded as an "
+                              + "identifier; it must be one.");
+        }
+        case (none[uint]) {
+            ret i;
+        }
+    }
+}
+
+fn subst_path(&ext_ctxt cx, &vec[@ast::expr] args, 
+              @vec[ident] param_names, &path_ p, ast_fold fld) -> path_ {
+    // Don't substitute into qualified names.
+    if (len(p.types) > 0u || len(p.idents) != 1u) { ret p; }
+    alt (position(p.idents.(0), *param_names)) {
+        case (some[uint](?idx)) {
+            alt (args.(idx).node) {
+                case (expr_path(?new_path)) {
+                    ret new_path.node;
+                }
+                case (_) {
+                    cx.span_fatal(args.(idx).span,
+                                "This argument is expanded as a path; "
+                                + "it must be one.");
+                }
+            }
+        }
+        case (none[uint]) { ret p; }
+    }
+}
+
+
+fn subst_expr(&ext_ctxt cx, &vec[@ast::expr] args, @vec[ident] param_names, 
+              &ast::expr_ e, ast_fold fld, 
+              fn(&ast::expr_, ast_fold) -> ast::expr_ orig) -> ast::expr_ {
+    ret alt(e) {
+        case (expr_path(?p)){
+            // Don't substitute into qualified names.
+            if (len(p.node.types) > 0u || len(p.node.idents) != 1u) { e }
+            alt (position(p.node.idents.(0), *param_names)) {
+                case (some[uint](?idx)) {
+                    args.(idx).node
+                }
+                case (none[uint]) { e }
+            }
+        }
+        case (_) { orig(e,fld) }
+    }
+}
+
+
+fn add_new_extension(&ext_ctxt cx, span sp, &vec[@ast::expr] args,
+                     option::t[str] body) -> tup(str, syntax_extension) {
+    if (len(args) < 2u) {
+        cx.span_fatal(sp, "malformed extension description");
+    }
+
+    fn generic_extension(&ext_ctxt cx, span sp, &vec[@ast::expr] args,
+                         option::t[str] body, @vec[ident] param_names,
+                         @ast::expr dest_form) -> @ast::expr {
+        if (len(args) != len(*param_names)) {
+            cx.span_fatal(sp, #fmt("extension expects %u arguments, got %u",
+                                 len(*param_names), len(args)));
+        }
+
+        auto afp = default_ast_fold();
+        auto f_pre = 
+            rec(fold_ident = bind subst_ident(cx, args, param_names, _, _),
+                fold_path = bind subst_path(cx, args, param_names, _, _),
+                fold_expr = bind subst_expr(cx, args, param_names, _, _,
+                                            afp.fold_expr)
+                with *afp);
+        auto f = make_fold(f_pre);
+        auto result = f.fold_expr(dest_form);
+        dummy_out(f); //temporary: kill circular reference
+        ret result;
+        
+    }
+
+    let vec[ident] param_names = vec::empty[ident]();
+    let uint idx = 1u;
+    while(1u+idx < len(args)) {
+        param_names +=
+            [expr_to_ident(cx, args.(idx),
+                           "this parameter name must be an identifier.")];
+        idx += 1u;
+    }
+
+    ret tup(expr_to_str(cx, args.(0), "first arg must be a literal string."),
+            normal(bind generic_extension(_,_,_,_,@param_names,
+                                          args.(len(args)-1u))));
+}
+
+
+
+//
+// Local Variables:
+// mode: rust
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
+// End:
+//
diff --git a/src/comp/front/parser.rs b/src/comp/front/parser.rs
index 90f8fedb6dce..c70dd354d088 100644
--- a/src/comp/front/parser.rs
+++ b/src/comp/front/parser.rs
@@ -963,10 +963,19 @@ fn expand_syntax_ext(&parser p, common::span sp, &ast::path path,
     auto extname = path.node.idents.(0);
     alt (p.get_syntax_expanders().find(extname)) {
         case (none) { p.fatal("unknown syntax expander: '" + extname + "'"); }
-        case (some(ext::x(?ext))) {
+        case (some(ext::normal(?ext))) {
             auto ext_cx = ext::mk_ctxt(p);
             ret ast::expr_ext(path, args, body, ext(ext_cx, sp, args, body));
         }
+        // because we have expansion inside parsing, new macros are only
+        // visible further down the file
+        case (some(ext::macro_defining(?ext))) {
+            auto ext_cx = ext::mk_ctxt(p);
+            auto name_and_extension = ext(ext_cx, sp, args, body);
+            p.get_syntax_expanders().insert(name_and_extension._0,
+                                            name_and_extension._1);
+            ret ast::expr_tup(vec::empty[ast::elt]());
+        }
     }
 }
 
diff --git a/src/comp/middle/resolve.rs b/src/comp/middle/resolve.rs
index 858c7ea66dfb..9b94be9f7d4b 100644
--- a/src/comp/middle/resolve.rs
+++ b/src/comp/middle/resolve.rs
@@ -597,8 +597,6 @@ fn lookup_in_scope(&env e, scopes sc, &span sp, &ident name, namespace ns) ->
    option::t[def] {
     fn in_scope(&env e, &span sp, &ident name, &scope s, namespace ns) ->
        option::t[def] {
-        //not recursing through globs
-
         alt (s) {
             case (scope_crate(?c)) {
                 ret lookup_in_local_mod(e, -1, sp, name, ns, inside);
diff --git a/src/comp/rustc.rc b/src/comp/rustc.rc
index 2adecfa13bb1..ac64e7068f2e 100644
--- a/src/comp/rustc.rc
+++ b/src/comp/rustc.rc
@@ -48,6 +48,7 @@ mod front {
     mod ext;
     mod extfmt;
     mod extenv;
+    mod extsimplext;
     mod fold;
     mod codemap;
     mod lexer;
diff --git a/src/lib/vec.rs b/src/lib/vec.rs
index 3be6c1ef9ad3..db57953a962c 100644
--- a/src/lib/vec.rs
+++ b/src/lib/vec.rs
@@ -228,6 +228,24 @@ fn find[T](fn(&T) -> bool  f, &vec[T] v) -> option::t[T] {
     ret none[T];
 }
 
+fn position[T](&T x, &array[T] v) -> option::t[uint] {
+    let uint i = 0u;
+    while (i < len(v)) {
+        if (x == v.(i)) { ret some[uint](i); }
+        i += 1u;
+    }
+    ret none[uint];
+}
+
+fn position_pred[T](fn (&T) -> bool f, &vec[T] v) -> option::t[uint] {
+    let uint i = 0u;
+    while (i < len(v)) {
+        if (f(v.(i))) { ret some[uint](i); }
+        i += 1u;
+    }
+    ret none[uint];
+}
+
 fn member[T](&T x, &array[T] v) -> bool {
     for (T elt in v) { if (x == elt) { ret true; } }
     ret false;
diff --git a/src/test/compile-fail/extenv-not-string-literal.rs b/src/test/compile-fail/extenv-not-string-literal.rs
index 885924c83781..7c082b42320f 100644
--- a/src/test/compile-fail/extenv-not-string-literal.rs
+++ b/src/test/compile-fail/extenv-not-string-literal.rs
@@ -1,4 +1,4 @@
-// error-pattern:malformed #env call
+// error-pattern:requires a string
 
 fn main() {
   #env(10);
diff --git a/src/test/compile-fail/simplext-2.rs b/src/test/compile-fail/simplext-2.rs
new file mode 100644
index 000000000000..f833d87c8a0d
--- /dev/null
+++ b/src/test/compile-fail/simplext-2.rs
@@ -0,0 +1,6 @@
+//error-pattern:expanded as an identifier
+fn main() {
+  #simplext("mylambda", x, body, {fn f(int x) -> int {ret body}; f});
+  
+  assert(#mylambda(y*1, y*2)(8) == 16);
+}
\ No newline at end of file
diff --git a/src/test/compile-fail/simplext.rs b/src/test/compile-fail/simplext.rs
new file mode 100644
index 000000000000..953f97d0581f
--- /dev/null
+++ b/src/test/compile-fail/simplext.rs
@@ -0,0 +1,7 @@
+//error-pattern:expects 0 arguments, got 16
+
+fn main() {
+  #simplext("trivial", 1*2*4*2*1);
+  
+  assert(#trivial(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) == 16);
+}
diff --git a/src/test/run-pass/lib-vec.rs b/src/test/run-pass/lib-vec.rs
index 9bcd098fc370..24adaaa5972e 100644
--- a/src/test/run-pass/lib-vec.rs
+++ b/src/test/run-pass/lib-vec.rs
@@ -1,9 +1,12 @@
 
 use std;
 
+import std::vec::*;
+import std::option;
+
 fn test_init_elt() {
-    let vec[uint] v = std::vec::init_elt[uint](5u, 3u);
-    assert (std::vec::len[uint](v) == 3u);
+    let vec[uint] v = init_elt[uint](5u, 3u);
+    assert (len[uint](v) == 3u);
     assert (v.(0) == 5u);
     assert (v.(1) == 5u);
     assert (v.(2) == 5u);
@@ -13,8 +16,8 @@ fn id(uint x) -> uint { ret x; }
 
 fn test_init_fn() {
     let fn(uint) -> uint  op = id;
-    let vec[uint] v = std::vec::init_fn[uint](op, 5u);
-    assert (std::vec::len[uint](v) == 5u);
+    let vec[uint] v = init_fn[uint](op, 5u);
+    assert (len[uint](v) == 5u);
     assert (v.(0) == 0u);
     assert (v.(1) == 1u);
     assert (v.(2) == 2u);
@@ -24,17 +27,17 @@ fn test_init_fn() {
 
 fn test_slice() {
     let vec[int] v = [1, 2, 3, 4, 5];
-    auto v2 = std::vec::slice[int](v, 2u, 4u);
-    assert (std::vec::len[int](v2) == 2u);
+    auto v2 = slice[int](v, 2u, 4u);
+    assert (len[int](v2) == 2u);
     assert (v2.(0) == 3);
     assert (v2.(1) == 4);
 }
 
 fn test_map() {
     fn square(&int x) -> int { ret x * x; }
-    let std::option::operator[int, int] op = square;
+    let option::operator[int, int] op = square;
     let vec[int] v = [1, 2, 3, 4, 5];
-    let vec[int] s = std::vec::map[int, int](op, v);
+    let vec[int] s = map[int, int](op, v);
     let int i = 0;
     while (i < 5) { assert (v.(i) * v.(i) == s.(i)); i += 1; }
 }
@@ -44,16 +47,16 @@ fn test_map2() {
     auto f = times;
     auto v0 = [1, 2, 3, 4, 5];
     auto v1 = [5, 4, 3, 2, 1];
-    auto u = std::vec::map2[int, int, int](f, v0, v1);
+    auto u = map2[int, int, int](f, v0, v1);
     auto i = 0;
     while (i < 5) { assert (v0.(i) * v1.(i) == u.(i)); i += 1; }
 }
 
 fn test_filter_map() {
-    fn halve(&int i) -> std::option::t[int] {
+    fn halve(&int i) -> option::t[int] {
         if (i % 2 == 0) {
-            ret std::option::some[int](i / 2);
-        } else { ret std::option::none[int]; }
+            ret option::some[int](i / 2);
+        } else { ret option::none[int]; }
     }
     fn halve_for_sure(&int i) -> int { ret i / 2; }
     let vec[int] all_even = [0, 2, 8, 6];
@@ -61,11 +64,31 @@ fn test_filter_map() {
     let vec[int] all_odd2 = [];
     let vec[int] mix = [9, 2, 6, 7, 1, 0, 0, 3];
     let vec[int] mix_dest = [1, 3, 0, 0];
-    assert (std::vec::filter_map(halve, all_even) ==
-                std::vec::map(halve_for_sure, all_even));
-    assert (std::vec::filter_map(halve, all_odd1) == std::vec::empty[int]());
-    assert (std::vec::filter_map(halve, all_odd2) == std::vec::empty[int]());
-    assert (std::vec::filter_map(halve, mix) == mix_dest);
+    assert (filter_map(halve, all_even) ==
+                map(halve_for_sure, all_even));
+    assert (filter_map(halve, all_odd1) == empty[int]());
+    assert (filter_map(halve, all_odd2) == empty[int]());
+    assert (filter_map(halve, mix) == mix_dest);
+}
+
+fn test_position() {
+  let vec[int] v1 = [1, 2, 3, 3, 2, 5];
+  assert (position(1, v1) == option::some[uint](0u));
+  assert (position(2, v1) == option::some[uint](1u));
+  assert (position(5, v1) == option::some[uint](5u));
+  assert (position(4, v1) == option::none[uint]);
+}
+
+fn test_position_pred() {
+  fn less_than_three(&int i) -> bool {
+    ret i <3;
+  }
+  fn is_eighteen(&int i) -> bool {
+    ret i == 18;
+  }
+  let vec[int] v1 = [5, 4, 3, 2, 1];
+  assert (position_pred(less_than_three, v1) == option::some[uint](3u));
+  assert (position_pred(is_eighteen, v1) == option::none[uint]);
 }
 
 fn main() {
@@ -75,4 +98,6 @@ fn main() {
     test_map();
     test_map2();
     test_filter_map();
+    test_position();
+    test_position_pred();
 }
\ No newline at end of file
diff --git a/src/test/run-pass/simplext-2.rs b/src/test/run-pass/simplext-2.rs
new file mode 100644
index 000000000000..c15d63e2e883
--- /dev/null
+++ b/src/test/run-pass/simplext-2.rs
@@ -0,0 +1,5 @@
+fn main() {
+  #simplext("mylambda", x, body, {fn f(int x) -> int {ret body}; f});
+  
+  assert(#mylambda(y,y*2)(8) == 16);
+}
\ No newline at end of file
diff --git a/src/test/run-pass/simplext-3.rs b/src/test/run-pass/simplext-3.rs
new file mode 100644
index 000000000000..ad1b10a00520
--- /dev/null
+++ b/src/test/run-pass/simplext-3.rs
@@ -0,0 +1,5 @@
+fn main() {
+  #simplext("trivial", 1*2*4*2*1);
+  
+  assert(#trivial() == 16);
+}
diff --git a/src/test/run-pass/simplext.rs b/src/test/run-pass/simplext.rs
new file mode 100644
index 000000000000..9ca42e8c8fee
--- /dev/null
+++ b/src/test/run-pass/simplext.rs
@@ -0,0 +1,4 @@
+fn main() {
+  #simplext("m1", a, a*4);
+  assert (#m1(2) == 8);  
+}
\ No newline at end of file