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What is the meaning of this statement: S A=$P(P,,2) I S?

Belinda
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Rachana
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2 Answers2

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This may not be valid syntax based on the MUMPS implementation. For example, Intersystem Cache will generate a syntax error, since the second parameter passed to the piece function is blank.

The $P or $PIECE(str, delim, num), function will return the num-th segment of str when delimited by delim. So, p("a^b^c","^",2) returns "b". When delim is the empty string, $P will return the empty string. However, there can be a difference between passing nothing and an empty string.

S A=$P(P,,2) says to set the variable A to the value returned by the piece function.

Finally, I S, says that if the value of variable S evaluates to true, continue executing the rest of this line. The I or IF command also has the side effect of setting the $T variable to 1 if the expression is true, or 0, if the expression is false. This is important if your line of code is followed by an else statement, which uses $T to determine whether the previous if statement returned false.

lecrank
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Brian Pellin
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  • Can't add anything, except that in MUMPS spaces have important meaning, the general syntax is: ..., so if there is no argument of a command, it is followed by two spaces: ... (Anyway, glad to see M users, or at least ex-users around here.) – ern0 Aug 19 '13 at 20:04
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It means 

Set A = $PIECE(P,,2)

$PIECE(string,delimiter,from) returns the substring which is the nth piece of string, where the integer n is specified by the from parameter, and pieces are separated by a delimiter. The delimiter is not returned.

The links to the documentation is here: http://docs.intersystems.com/cache20102/csp/docbook/DocBook.UI.Page.cls?KEY=RCOS_fpiece

rkg
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