st: New package -moss- available from SSC

[Robert Picard <picard@netbox.com>]

Thanks to Kit Baum, a new package -moss-, coauthored with Nick Cox, is
now available from SSC. -moss- finds multiple occurrences of
substrings. To install, type:

ssc install moss

-moss- can be used to search for a simple pattern of text. For example:

moss mystrvar, match("hello")

will find all occurrences of "hello" for each observations of the
string variable mystrvar.  -moss- creates a variable with the count of
occurrences and as many variables as necessary to indicate the
position of each match.

-moss- can also be used to search for more complex patterns of text
using regular expressions. With the -regex- option, -moss- creates
additional variables for each subexpression matched. For example, to
find all occurrences of one or more digits:

. moss mystrvar, match("([0-9]+)") regex

To find runs of the letter X:

. moss history, match("(X+)") regex

To match anything delimited by commas:

. moss mystrvar, match("([^,]+)") regex

-moss- is the result of a collaboration between Nick Cox and myself
that stemmed from a Statalist query by Rebecca Pope about finding the
position of the longest run of "X" within a string variable.

Cheers.

Robert
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