当我执行以下测试程序时:
let re = Str.regexp "{\\(foo\\)\\(bar\\)?}"
let check s =
try
let n = Str.search_forward re s 0 in
let a = Str.matched_group 1 s in
let b = Str.matched_group 2 s in
Printf.printf "'%s' => n=%d, a='%s', b='%s'\n" s n a b
with
_ -> Printf.printf "'%s' => not found\n" s
let _ =
check "{foo}";
check "{foobar}"
我得到奇怪的结果。即:
$ ocaml str.cma test.ml'{foo}'=>找不到'{foobar}'=> n = 0,a ='foo',b ='bar'
通过\\(
和\\)
进行分组是否与?
运算符不兼容?文档未提及此。
对于您的第一个示例,组2不匹配。因此对Str.matched_group 2
的调用引发了Not_found
。
我这样重写了您的check
函数:
let check s =
let check1 n g =
try
let m = Str.matched_group g s in
Printf.printf "'%s' group %d => n = %d, match = '%s'\n"
s g n m
with Not_found ->
Printf.printf "'%s' group %d => not matched\n" s g
in
let n = Str.search_forward re s 0 in
check1 n 1;
check1 n 2
以下是修改后的代码的输出:
'{foo}' group 1 => n = 0, match = 'foo'
'{foo}' group 2 => not matched
'{foobar}' group 1 => n = 0, match = 'foo'
'{foobar}' group 2 => n = 0, match = 'bar'