Document all macros, remove unsupported tests. (google#101)

doc/langdef.md

@@ -629,6 +629,17 @@ macros are:
     if the predicate of exactly one element/key evaluates to `true`, and the
     rest to `false`. Any other combination of boolean results evaluates to
     `false`, and any predicate error causes the macro to raise an error.
+*   `e.map(x, t)` transforms a list `e` by taking each element `x` to the
+    element given by the expression `t`, which can use the variable `x`. For
+    instance, `[1, 2, 3].map(n, n * n)` evaluates to `[1, 4, 9]`.  Any
+    evaluation error for any element causes the macro to raise an error.  The
+    `map()` macro is not supported when `e` is a map.
+*   `e.filter(x, p)` returns the sublist of all elements `x` of list `e` which
+    evaluate to `true` in the predicate expression `p` (which can use variable
+    `x`).  For instance, `[1, 2, 3].filter(i, i % 2 > 0)` evaluates to `[1, 3]`.
+    If no elements evaluate to `true`, the result is an empty list. Any
+    evaluation error for any element causes the macro to raise an error. The
+    `filter()` macro is not supported on maps.
 
 ### Field Selection
 

tests/simple/testdata/macros.textproto

@@ -207,16 +207,7 @@ section {
       errors: { message: "divide by zero" }
     }
   }
-  test {
-    name: "map_many"
-    expr: "{1: 1, 2: 4, 3: 9}.map(x, x * x)"
-    value: { list_value {
-        values: { int64_value: 1 }
-        values: { int64_value: 4 }
-        values: { int64_value: 9 }
-      }
-    }
-  }
+  # The map() macro is currently not supported for maps.
 }
 section {
   name: "filter"
@@ -270,13 +261,5 @@ section {
       errors: { message: "divide by zero" }
     }
   }
-  test {
-    name: "map_some"
-    expr: "{0: 10, 1: 11, 2: 12, 3: 13, 4: 14}.filter(x, x % 2 == 1)"
-    value: { list_value {
-        values: { int64_value: 1 }
-        values: { int64_value: 3 }
-      }
-    }
-  }
+  # The filter() macro is currently not supported for maps.
 }