diff options
| -rw-r--r-- | ChangeLog | 16 | ||||
| -rw-r--r-- | eval.c | 25 | ||||
| -rw-r--r-- | txr.1 | 13 |
3 files changed, 42 insertions, 12 deletions
@@ -1,5 +1,21 @@ 2015-04-25 Kaz Kylheku <kaz@kylheku.com> + Allow (force ...) to be an assignable place. + + This allows mlet variables to be assignable. + + * eval.c (force_s): New global variable. + (op_modplace): Handle force form. + (me_mlet): Use force_s symbol. + (force_l): New static function. + (eval_init): Initialize force_s variable. Use it in registration + of force function. + + * txr.1: Remove text in mlet definition that variables + are not assignable. Replace with note about an unspecified behavior. + +2015-04-25 Kaz Kylheku <kaz@kylheku.com> + Introducing mlet macro. * eval.c (me_mlet): New static function. @@ -79,7 +79,7 @@ val dohash_s; val uw_protect_s, return_s, return_from_s; val list_s, append_s, apply_s, iapply_s; val gen_s, gun_s, generate_s, rest_s, plus_s; -val promise_s, promise_forced_s, promise_inprogress_s; +val promise_s, promise_forced_s, promise_inprogress_s, force_s; val op_s, ap_s, identity_s, apf_s, ipf_s; val ret_s, aret_s; val hash_lit_s, hash_construct_s; @@ -1809,6 +1809,8 @@ static loc dwim_loc(val form, val env, val op, val newform, val *retval) return nulloc; } +static loc force_l(val promise); + static val op_modplace(val form, val env) { uses_or2; @@ -1864,6 +1866,9 @@ static val op_modplace(val form, val env) val vec = eval(second(place), env, form); val ind = eval(third(place), env, form); ptr = vecref_l(vec, ind); + } else if (sym == force_s) { + val promise = eval(second(place), env, form); + ptr = force_l(promise); } else { eval_error(form, lit("~s: ~s is not a recognized place form"), op, place, nao); @@ -2888,7 +2893,6 @@ static val me_mlet(val form, val menv) val bindings = pop(&body); val symacrolet = intern(lit("symacrolet"), user_package); val delay = intern(lit("delay"), user_package); - val force = intern(lit("force"), user_package); list_collect_decl (ordinary_syms, ptail_osyms); list_collect_decl (syms, ptail_syms); @@ -2919,7 +2923,7 @@ static val me_mlet(val form, val menv) ptail_inits = list_collect(ptail_inits, init); ptail_gensyms = list_collect(ptail_gensyms, gen); ptail_smacs = list_collect(ptail_smacs, - list(sym, list(force, gen, nao), nao)); + list(sym, list(force_s, gen, nao), nao)); ptail_sets = list_collect(ptail_sets, list(set_s, gen, list(delay, init, nao), nao)); @@ -3716,6 +3720,18 @@ static val force(val promise) } } +static loc force_l(val promise) +{ + loc pstate = car_l(promise); + val cd = cdr(promise); + loc pval = car_l(cd); + + if (deref(pstate) != promise_forced_s) + force(promise); + + return pval; +} + static void reg_op(val sym, opfun_t fun) { assert (sym != 0); @@ -3975,6 +3991,7 @@ void eval_init(void) promise_s = intern(lit("promise"), system_package); promise_forced_s = intern(lit("promise-forced"), system_package); promise_inprogress_s = intern(lit("promise-inprogress"), system_package); + force_s = intern(lit("force"), user_package); op_s = intern(lit("op"), user_package); ap_s = intern(lit("ap"), user_package); do_s = intern(lit("do"), user_package); @@ -4523,7 +4540,7 @@ void eval_init(void) reg_fun(intern(lit("repeat"), user_package), func_n2o(repeat, 1)); reg_fun(intern(lit("pad"), user_package), func_n3o(pad, 1)); reg_fun(intern(lit("weave"), user_package), func_n0v(weavev)); - reg_fun(intern(lit("force"), user_package), func_n1(force)); + reg_fun(force_s, func_n1(force)); reg_fun(intern(lit("rperm"), user_package), func_n2(rperm)); reg_fun(intern(lit("perm"), user_package), func_n2o(perm, 1)); reg_fun(intern(lit("comb"), user_package), func_n2(comb)); @@ -15570,14 +15570,11 @@ construct, then its .meta init-form is never evaluated. -Any -.meta sym -which has no initializer is an ordinary variable. It is initialized -immediately with the value -.code nil -and may be assigned. Those -.metn sym -s -which have initializers may not be assigned. +The bound variables may be assigned. If, before initialization, a variable is +updated in such a way that its prior value is not needed, it is unspecified +whether initialization takes place, and thus whether its +.meta init-form +is evaluated. Direct circular references erroneous and are diagnosed. |