diff options
| -rw-r--r-- | eval.c | 12 | ||||
| -rw-r--r-- | txr.1 | 21 |
2 files changed, 33 insertions, 0 deletions
@@ -3786,6 +3786,17 @@ static val weavev(struct args *args) return lazy_appendl(generate(whil, gen)); } +static val promisep(val obj) +{ + if (consp(obj)) { + val sym = car(obj); + if (sym == promise_s || sym == promise_forced_s) + return t; + } + + return nil; +} + static val force(val promise) { loc pstate = car_l(promise); @@ -4692,6 +4703,7 @@ void eval_init(void) reg_fun(intern(lit("pad"), user_package), func_n3o(pad, 1)); reg_fun(intern(lit("weave"), user_package), func_n0v(weavev)); reg_fun(force_s, func_n1(force)); + reg_fun(intern(lit("promisep"), user_package), func_n1(promisep)); 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)); @@ -15624,6 +15624,27 @@ the promise will take on the value of .meta expression or the assigned value. +.coNP Function @ promisep +.synb +.mets (promisep << object ) +.syne +.desc +The +.code promisep +function returns +.code t +if +.meta object +is a promise object: an object created by the +.code delay +macro. Otherwise it returns +.codn nil . + +Note: promise objects are conses. The +.code typeof +function applied to a promise returns +.codn cons . + .coNP Macro @ mlet .synb .mets (mlet >> ({ sym | >> ( sym << init-form )}*) << body-form *) |