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| -rwxr-xr-x | doc/manual.txt | 53 | ||||
| -rwxr-xr-x | todo.txt | 4 |
2 files changed, 55 insertions, 2 deletions
diff --git a/doc/manual.txt b/doc/manual.txt index ee275fbce..e0fee2a31 100755 --- a/doc/manual.txt +++ b/doc/manual.txt @@ -3149,6 +3149,59 @@ The macro call expands to: write(stdout, "x") write(stdout, ": ") writeln(stdout, x) + + +Bind in macros +~~~~~~~~~~~~~~ + +The above ``debug`` macro relies on the fact that ``write``, ``writeln`` and +``stdout`` are declared in the system module and thus visible in the +instantiating context. There is a way to use bound identifiers +(aka `symbols`:idx) instead of using unbound identifiers. The ``bind`` +statement plus the ``bindSym`` builtin can be used for that: + +.. code-block:: nimrod + # to work with Nimrod syntax trees, we need an API that is defined in the + # ``macros`` module: + import macros + + macro debug(n: expr): stmt = + # we need to declare the used symbols here: + bind write, writeln, stdout + result = newNimNode(nnkStmtList, n) + # iterate over any argument that is passed to this macro: + for i in 1..n.len-1: + # we can access the bound symbol via 'bindSym': + add(result, newCall(bindSym"write", bindSym"stdout", toStrLit(n[i]))) + add(result, newCall(bindSym"write", bindSym"stdout", newStrLitNode(": "))) + add(result, newCall(bindSym"writeln", bindSym"stdout", n[i])) + + var + a: array [0..10, int] + x = "some string" + a[0] = 42 + a[1] = 45 + + debug(a[0], a[1], x) + +The macro call expands to: + +.. code-block:: nimrod + write(stdout, "a[0]") + write(stdout, ": ") + writeln(stdout, a[0]) + + write(stdout, "a[1]") + write(stdout, ": ") + writeln(stdout, a[1]) + + write(stdout, "x") + write(stdout, ": ") + writeln(stdout, x) + +However, the symbols ``write``, ``writeln`` and ``stdout`` are already bound +and are not looked up again. As the example shows, ``bind`` does work with +overloaded symbols implicitely. Statement Macros diff --git a/todo.txt b/todo.txt index 254fbf7b7..c49e80980 100755 --- a/todo.txt +++ b/todo.txt @@ -1,9 +1,7 @@ version 0.9.0 ============= -- document 'bind' for macros - ``final`` should be the default for objects -- make 'bind' default for templates and introduce 'mixin' - implement "closure tuple consists of a single 'ref'" optimization - implement for loop transformation for first class iterators @@ -30,6 +28,8 @@ Bugs version 0.9.XX ============== +- make 'bind' default for templates and introduce 'mixin' +- distinguish between open and closed nkSymChoice - JS gen: - fix exception handling |