Add quasiquote expression

1 files changed, 21 insertions, 0 deletions

diff --git a/doc/concepts/expressions.md b/doc/concepts/expressions.md
index c5d120e4..aaea3d27 100644
--- a/doc/concepts/expressions.md
+++ b/doc/concepts/expressions.md
@@ -79,6 +79,27 @@ evaluation.
 The value is the value of the key `"$1"` uninterpreted, if present,
 and `null` otherwise.
 
+##### Quasi-Quoting: ``"`"``
+
+The value is the value of the key `"$1"` uninterpreted but replacing
+all outermost maps having a key `"type"` with the value either
+`","` or `",@"` in the following way.
+ - If the value for the key `"type"` is `","`, the value for the
+   key `"$1"` (or `null` if there is no key `"$1"`) is evaluated
+   and the map is replaced by the value of that evaluation.
+ - If the value for the key `"type"` is `",@"` it is an error if
+   that map is not an entry of a literal list. The value for the
+   key `"$1"` (or `[]` if there is no key `"$1"`) is evaluated;
+   the result of that evaluation has to be a list. The entries of
+   that list (i.e., the list obtained by evaluating the value for
+   `"$1"`) are inserted (not the list itself) into the surrounding
+   list replacing that map.
+For example, ``{"type": "`", "$1": [1, 2, {"type": ",@", "$1": [3, 4]}]}``
+evaluates to `[1, 2, 3, 4]` while
+``{"type": "`", "$1": [1, 2, {"type": ",", "$1": [3, 4]}]}``
+evaluates to `[1, 2, [3, 4]]`.
+
+
 ##### Sequential binding: `"let*"`
 
 The key `"bindings"` (default `[]`) has to be (syntactically) a