我有兴趣搜索很多长串,尝试在rebol中破解类似sed的实用程序作为学习练习.作为一个婴儿步骤,我决定寻找一个角色:
>> STR: "abcdefghijklmopqrz"
>> pos: index? find STR "z"
== 18
>> pos
== 18
大!我们来寻找其他东西......
>> pos: index? find STR "n"
** Script Error: index? expected series argument of type: series port
** Where: halt-view
** Near: pos: index? find STR "n"
>> pos
== 18
什么？:-(
是的,我正在搜索的字符串中没有"n".但是解释器爆炸而不是做一些明智的事情有什么好处,例如在pos中返回一个可测试的"null"字符？
我被告知我应该这样做:
>> if found? find STR "z" [pos: index? find STR "z"]
== 18
>> if found? find STR "n" [pos: index? find STR "n"]
== none
>> pos
== …