regexp Go lang中的错误

Question

I'm trying to use this regular expressions in Go lang:

~((?<=^[^\s])|(?<=\s[^\s]))\s(?=[^\s](\s|$))~

{(c|d|e|i|l|n|o|p|r|t|z)\1+}

{( |a|b|d|[f-h]|i|[j-k]|m|q|s|[u-y])\1+}

{(c|d|e|i|l|n|o|p|r|t|z)\1+}

{( |a|b|[f-h]|i|[j-k]|m|q|s|[u-y])\1+}

{(si|sa|za|ja|to)\1+}

and in everyone of those i get this error:

panic: regexp: Compile(~((?<=^[^\s])|(?<=\s[^\s]))\s(?=[^\s](\s|$))~): error parsing regexp: invalid or unsupported Perl syntax: (?<

Maybe there is a trick know for someone? :/ or is it impossible to use them?

Answer 1

If no lookbehinds supported, use a workaround like this:

((^|\s)\S)(\s)(?=\S(\s|$))

where:

Capture group 1 contains what's to be written back in place of the
lookbehind.

Capture group 3 is the actual whitespace in question.
It's in a capture group just to separate it from the entire match.

Summary: Group 1 + Group 3 = entire match.

Expanded:

 #  (                             # (1 start)
 #       (?<= ^ [^\s] )
 #    |  (?<= \s [^\s] )
 #  )                             # (1 end)

 (                             # (1 start)
      ( ^ | \s )                    # (2)
      \S 
 )                             # (1 end)
 ( \s )                        # (3)
 (?=
      \S 
      ( \s | $ )                    # (4)
 )