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Re: st: extended function: piece
Adrian Mander <Adrian.P.Mander@gsk.com> asks:
> Any reason why piece doesn't appear to allow the length of pieces
> to be 1?
> . local subpiece: piece 2 1 of "abcdefghi"
> invalid syntax
> SYNTAX: piece #piece_number #length_of_pieces of [`]"string"['] [,
> nobreak ]
> <-- no restriction is mentioned on the STATA help system.
> And is piece going to be computationally faster than substr?
Answering last question first: the -substr()- function will be
faster. It doesn't have to worry about all the logic that
-piece- goes through to determine appropriate breaks.
Now to the first question. The -piece- macro extended function
was designed for cases where a programmer is trying to produce
output that is to fit within a certain width and the text is
allowed to wrap, but it would be nice for the text to break to a
new line at word boundaries instead of in the middle of a word if
possible. Since the advent of -smcl- in Stata, the -piece- macro
function is seldom needed.
-piece- was never meant to be used in a manner similar to
-substr()-. Even if we changed the code for -piece- to allow the
"#length_of_pieces" to be 1, it may not be what you are really
wanting. Think in terms of what it does with spaces.
. local a : piece 2 3 of "abc d efg"
. di "|`a'|"
This is a feature of -piece-. It will treat multiple spaces as
one space and trim off leading and trailing spaces for the
result. This is most often what is wanted when trying to use
-piece- for producing a (possibly) wrapped text output.
We should update the documentation to indicate that 2 is the
minimal "#length_of_piece" allowed.
If you want to provide more context for the overall task you are
trying to accomplish, maybe someone will be able to suggest a
Ken Higbee email@example.com
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