Regular Expressions to Split Lists Into Sub-Lists

[Yimin Rong]

For example, given a string "A, B, C (P, Q, R), D (X, Y [K, L, M ,N],
Z)".

Would like to split into tokens thusly:

a[0] == "A"
a[1] == "B"
a[2] == "C (P, Q, R)"
a[3] == "D (X, Y [K, L, M ,N], Z)"

i.e. do not descend into sub-lists

PHP split() using commas as a delimiter will give 14 tokens.

I can write a routine which checks the input byte by byte and
increments or decrements a counter based on how many opening "( [ {"
or closing ") ] }" brackets it sees. If counter 0, this means ignore
delimiters (i.e. keep looking). Guaranteed to work, but to my mind
seems to be rather clunky.

Is it possible to extract the tokens using regular expressions? E.g.
substitute highest level commas with a special delimiter say "~", and
split using that delimiter.

Thanks for reading.

Regards,

YR

[Curtis]

Yimin Rong wrote:

For example, given a string "A, B, C (P, Q, R), D (X, Y [K, L, M ,N],
Z)".

Would like to split into tokens thusly:

a[0] == "A"
a[1] == "B"
a[2] == "C (P, Q, R)"
a[3] == "D (X, Y [K, L, M ,N], Z)"

i.e. do not descend into sub-lists

PHP split() using commas as a delimiter will give 14 tokens.

I can write a routine which checks the input byte by byte and
increments or decrements a counter based on how many opening "( [ {"
or closing ") ] }" brackets it sees. If counter 0, this means ignore
delimiters (i.e. keep looking). Guaranteed to work, but to my mind
seems to be rather clunky.

Is it possible to extract the tokens using regular expressions? E.g.
substitute highest level commas with a special delimiter say "~", and
split using that delimiter.

Seems like you already have your answer here. If the delimiters for
the top-level are different, it shouldn't be a problem to split on them.

--
Curtis

[Yimin Rong]

On Aug 17, 6:29 pm, Curtis <dye...@gmail.c omwrote:

Yimin Rong wrote:

For example, given a string "A, B, C (P, Q, R), D (X, Y [K, L, M ,N],
Z)".

Would like tosplitinto tokens thusly:

a[0] == "A"
a[1] == "B"
a[2] == "C (P, Q, R)"
a[3] == "D (X, Y [K, L, M ,N], Z)"

i.e. do not descend into sub-lists

PHPsplit() using commas as a delimiter will give 14 tokens.

I can write a routine which checks the input byte by byte and
increments or decrements a counter based on how many opening "( [ {"
or closing ") ] }" brackets it sees. If counter 0, this means ignore
delimiters (i.e. keep looking). Guaranteed to work, but to my mind
seems to be rather clunky.

Is it possible to extract the tokens using regular expressions? E.g.
substitute highest level commas with a special delimiter say "~", and
splitusing that delimiter.

Seems like you already have your answer here. If the delimiters for
the top-level are different, it shouldn't be a problem tospliton them.

--
Curtis

Agreed, however the step I need is to replace top level delimiters in
the input. Do you think regular expression substitution can do this? /
YR