Introducing optional arguments.

* debug.c (help, show_bindings): put_string arguments reversed.

* eval.c (bind_args): Support colon notation in interpreted
function lambda lists for optional arguments. Improved error checking.
(apply): Allow optional arguments to be left out.
(dwim_loc): Reversed arguments to replace_str, replace_vec,
replace_list.
(eval_init): Numerous intrinsics now have arguments that are optional.
New function rand introduced which reverses arguments relative to
random. New intrinsic function hash introduced for alternative
construction of hashes.

* gc.c (sweep): Reversed arguments to put_char.

* hash.c (weak_keys_k, weak_vals_k, equal_based_k): New keyword
symbol variables.
(hashv): New function.
(hash_init): Intern new symbols.

* hash.h (weak_keys_k, weak_vals_k, equal_based_k, hashv): Declared.

* lib.c (colon_k): New keyword symbol variable.
(replace_list, replace_str, replace_vec): Arguments rearranged.
(tree_find): testfun becomes optional argument.
(int_str): base becomes optional argument.
(func_f0, func_f1, func_f2, func_f3, func_f4, func_n0,
func_n1, func_n2, func_n3, func_n4,  func_f0v, func_f1v,
func_f2v, func_f3v, func_f4v, func_n0v, func_n1v,
func_n2v, func_n3v, func_n4v, func_interp): Initialize optargs to zero.
(func_n0o, func_n1o, func_n2o, func_n3o, func_n4o): New functions.
(cobj_print_op): Reversed arguments to put_string.
(find): testfun and keyfun become optional arguments.
(replace): Parameters rearranged and arguments rearranged in calls to
replace_list, replace_str and replace_vec.
(obj_init): colon_k initialized.
(obj_print, obj_pprint): Arguments reversed, and stream defaults
to std_output. Arguments reversed in calls to put_char and put_string.
(dump): Arguments reversed in call to put_char.

* lib.h (struct func): sizes of minparam, fixparam bitfields
adjusted. New bitfield optargs. New unnamed bitfield added so
the previous ones add up to 16 bits.
(colon_k): Declared.
(func_n0o, func_n1o, func_n2o, func_n3o, func_n4o): Declared.
(replace_list, replace_str, replace_vec, replace): Declarations updated.

* match.c (debuglf, dump_shell_string, dump_byte_string, dump_var,
do_output_line, extract): Reversed arguments to put_char and

1 files changed, 18 insertions, 6 deletions

diff --git a/txr.1 b/txr.1
index 636c8aba..25e6d8b6 100644
--- a/txr.1
+++ b/txr.1
@@ -4606,6 +4606,11 @@ The dotted notation can be used to write a function that accepts
 a variable number of arguments. To write a function that accepts
 variable arguments only, with no required arguments, use a single symbol.
 
+The keyword symbol : can appear in the parameter list. It is not an argument,
+but a separator between required parameters and optional parameters.
+When the function is called, optional parameter for which arguments
+are not supplied take on the value nil.
+
 Functions created by lambda capture the surrounding variable bindings.
 
 
@@ -4628,6 +4633,11 @@ Variadic funcion:
 
   (lambda args (list 'my-list-of-arguments args))
 
+Optional arguments:
+
+  [(lambda (x : y) (list x y)) 1] -> (1 nil)
+  [(lambda (x : y) (list x y)) 1 2] -> (1 2)
+
 .SS Operator op
 
 .TP
@@ -4855,11 +4865,13 @@ Syntax:
 Description:
 
 The defun operator introduces a new function in the global function namespace.
-The function is similar to a lambda, except that <body-form>-s are surrounded
-by a named block called nil. The name of this block is the same as the name of
-the function, making it possible to terminate the function and return a
-value using (return-from <name> <value>). For more information, see the
-definition of the block operator.
+The function is similar to a lambda, and has the same parameter syntax
+and semantics as the lambda operator.
+
+Unlike in lambda, the <body-form>-s of a defun are surrounded by a block.
+The name of this block is the same as the name of the function, making it
+possible to terminate the function and return a value using (return-from <name>
+<value>). For more information, see the definition of the block operator.
 
 A function may call itself by name, allowing for recursion.
 
@@ -6430,7 +6442,7 @@ Certain object types have a custom equal function.
 
 .SS Functions search-regex and match-regex
 
-.SS Function make-hash
+.SS Functions make-hash, hash
 
 .SS Function sethash