Implementing #H((...) ...) read/print syntax for hash tables.

* hash.c (print_key_val, hash_print_op): New static functions.
(hash_ops): hash_print_op wired in in place of cobj_print_op.

* parser.l (HASH_H): New token recognized.

* parser.y (HASH_H): New terminal symbol.
(hash): New nonterminal symbol.
(expr): Acquires hash as a constituent.
(hash_from_notation): New static function.

* txr.1: Hash syntax described.

* txr.vim: Updated.

1 files changed, 13 insertions, 1 deletions

diff --git a/txr.1 b/txr.1
index b51813d2..45718727 100644
--- a/txr.1
+++ b/txr.1
@@ -4476,6 +4476,7 @@ list, which terminates nonempty lists.
 
 Function and variable bindings are dynamically scoped in TXR Lisp. However,
 closures do capture variables.
+
 .SS Additional Syntax
 
 Much of the TXR Lisp syntax has been introduced in the previous sections of the
@@ -4542,11 +4543,22 @@ and not a quasiquote.
 
 .SS Vectors
 
-.IP #(...)
+.IP "#(...)"
 
 A hash token followed by a list denotes a vector. For example #(1 2 a)
 is a three-element vector containing the numbers 1 and 2, and the symbol a.
 
+.SS Hashes
+
+.IP "#H((<hash-argument>*) (<key> <value>)*)"
+
+The notation #H followed by a nested list syntax denotes a hash table literal.
+The first item in the syntax is a list of keywords. These are the same
+keywords as are used when calling the function hash to construct
+a hash table. Allowed keywords are: :equal-based, :weak-keys, :weak-values.
+An empty list can be specified as nil or (), which defaults to a
+hash table basd on the eq function, with no weak semantics.
+
 .SS Nested Quotes
 
 Quotes can be nested.  What if it is necessary to unquote something in the