diff options
| -rw-r--r-- | ChangeLog | 8 | ||||
| -rw-r--r-- | eval.c | 9 | ||||
| -rw-r--r-- | txr.1 | 16 |
3 files changed, 32 insertions, 1 deletions
@@ -1,3 +1,11 @@ +2011-12-07 Kaz Kylheku <kaz@kylheku.com> + + * eval.c (progn_s): New symbol variable. + (op_progn): New static function. + (eval_init): Initialize new variable, register progn operator. + + * txr.1: progn documented. + 2011-12-06 Kaz Kylheku <kaz@kylheku.com> Version 046 @@ -50,7 +50,7 @@ val top_vb, top_fb; val op_table; val eval_error_s; -val let_s, let_star_s, lambda_s, call_s; +val progn_s, let_s, let_star_s, lambda_s, call_s; val cond_s, if_s, and_s, or_s, defvar_s, defun_s; val inc_s, dec_s, push_s, pop_s, gethash_s, car_s, cdr_s; val for_s, for_star_s, dohash_s, uw_protect_s, return_s, return_from_s; @@ -400,6 +400,11 @@ static val bindings_helper(val vars, val env, val sequential, val ctx_form) return new_bindings; } +static val op_progn(val form, val env) +{ + return eval_progn(rest(form), env, form); +} + static val op_let(val form, val env) { val let = first(form); @@ -992,6 +997,7 @@ void eval_init(void) top_vb = make_hash(t, nil, nil); op_table = make_hash(nil, nil, nil); + progn_s = intern(lit("progn"), user_package); let_s = intern(lit("let"), user_package); let_star_s = intern(lit("let*"), user_package); lambda_s = intern(lit("lambda"), user_package); @@ -1025,6 +1031,7 @@ void eval_init(void) sethash(op_table, qquote_s, cptr((mem_t *) op_qquote_error)); sethash(op_table, unquote_s, cptr((mem_t *) op_unquote_error)); sethash(op_table, splice_s, cptr((mem_t *) op_unquote_error)); + sethash(op_table, progn_s, cptr((mem_t *) op_progn)); sethash(op_table, let_s, cptr((mem_t *) op_let)); sethash(op_table, let_star_s, cptr((mem_t *) op_let)); sethash(op_table, lambda_s, cptr((mem_t *) op_lambda)); @@ -4322,6 +4322,22 @@ alternative1 | alternative2 | ... | alternativeN Multiple syntactic variations allowed in one place are indicated as bar-separated items. +.SS Operator progn + +.TP +Syntax: +(progn <form>*) + +.TP +Description + +The progn operator evaluates forms in order, and returns the value +of the last form. The return value of (progn) is nil. + +Various other operators such as let also arrange for the evaluation +of a body of forms, the value of the last of which is returned. +These operators are said to feature an "implicit progn". + .SS Operators let and let* .TP |