如何从承诺中退出承诺?
发布时间:2020-12-15 21:49:40 所属栏目:大数据 来源:网络整理
导读:如何从承诺中退出承诺? perl6文档不提供简单的方法.例如: my $x = start { loop { # loop forever until "quit" is seen my $y = prompt("Say something: "); if $y ~~ / quit / { # I want to exit the promise from here; # "break" and "this.break" ar
如何从承诺中退出承诺? perl6文档不提供简单的方法.例如:
my $x = start { loop { # loop forever until "quit" is seen my $y = prompt("Say something: "); if $y ~~ / quit / { # I want to exit the promise from here; # "break" and "this.break" are not defined; # "return" does not break the promise; # I do NOT want an error exception when exiting a promise; # I want to return a value as the result of this promise; } else { say $y; } } } 我不想永远处于承诺循环中. break()和this.break()无法识别,返回不会破坏承诺. 解决方法
使用
last keyword退出循环.
保持的起始块值是其最后一个语句返回的值. 所以: my $x = start { loop { # loop forever until "quit" is seen my $y = prompt("Say something: "); if $y ~~ / quit / { last } else { say $y; } } 42 # <-- The promise will be kept with value `42` } (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |