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$PIECE

M[UMPS] by Example

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Introduced in the 1977 ANSI M[UMPS] language standard.

This function returns a substring of the value passed as a parameter.

Set X="ABC*DEF"

Reference   Value
$Piece(X,"*",1)   "ABC"
$Piece(X,"*",2)   "DEF"
$Piece(X,"*",3)   "" (empty string)
$Piece(X,"B",1)   "A"

Set Y="B"

Reference   Value
$Piece(X,Y,1)   "A"
$Piece(X,Y,2)   "C*DEF"
$Piece(X,"/",1)   "ABC*DEF"

Set X="A.B.C.D"

Reference   Value
$Piece(X,".",1)   "A"
$Piece(X,".",2,3)   "B.C"
$Piece(X,".",1,100)   "A.B.C.D"
$Piece(X,".",–5,2)   "A.B"
$Piece(X,".",3,2)   ""
$Piece(X,"",1,100)   ""

Addition in the 1984 ANSI M[UMPS] language standard.

It is allowed to specify a reference to $Piece on the left hand side of the equal sign in a Set command.

Set ^DATA("SUB")="11^22^33^44^55"

Reference   Value
Set $Piece(^DATA("SUB"),"^",3)=123   "11^22^123^44^55"
Set $Piece(^DATA("SUB"),"^",3,4)="three^four"   "11^22^three^four^55"
Set $Piece(^DATA("SUB"),"^",3)="a^b^c"   "11^22^a^b^c^four^55"
Set $Piece(^DATA("SUB"),"^",2,4)=""   "11^^c^four^55"

Set X="This is an test"

Reference   Value
Set $Piece(x," ",3)="a"   X="This is a test"
Set $Piece(x," ",2,3)="was no"   X="This was no test"
Set $Piece(x," ",3)="a"   X="This was a test"

Kill ^X
Set ^X(1,2,3)=9
Set ^X(1,2)=7
Set $Piece(^(2),";",3,^X(1,2,3))=6
Write ^(2)
Let’s trace the order of evaluation, and see what happens to the naked indicator:
Set ^X(1,2,3)=9
naked indicator is ^X(1,2,
Set ^X(1,2)=7
naked indicator is ^X(1,

fetch ^X(1,2,3); naked indicator is ^X(1,2,
fetch ^(2) = ^X(1,2,2), which is ‘undefined’ (error: M7)

So, let’s resolve that problem:
Kill ^X
Set ^X(1,2,3)=9
Set ^X(1,2,2)=8
Set ^X(1,2)=7
Set $Piece(^(2),";",3,^X(1,2,3))=6
Write ^(2)
Now that all referenced variables are defined, the command is evaluated
as:
Set $Piece(^X(1,2,2),";",3,9)=6
so that the value of ^X(1,2,2) becomes "8;;6"

Set ^X("Y")=1
Set $Piece(^X("Y"),";",2,1)=0
Write ^X("Y")
will produce the value 1. Because in the Set $Piece, the until value is less than the from value, no information is changed, and the naked indicator is unaffected.

Examples with naked references:

$Piece(VALUE,STRING)
Set ^ABC(1,2)="reset naked indicator"
; naked indicator is now ^ABC(1,
Set ^(3,4)=$Piece(^(5,6),^(7,8))
; 1. fetch ^(5,6) = ^ABC(1,5,6)
; 2. fetch ^(7,8) = ^ABC(1,5,7,8)
; 3. store ^(3,4) = ^ABC(1,5,7,3,4)
; naked indicator is now: ^ABC(1,5,7,3,

$Piece(VALUE,STRING,PIECE)
Set ^ABC(1,2)="reset naked indicator"
; naked indicator is now ^ABC(1,
Set ^(3,4)=$Piece(^(5,6),^(7,8),^(9,10))
; 1. fetch ^(5,6) = ^ABC(1,5,6)
; 2. fetch ^(7,8) = ^ABC(1,5,7,8)
; 3. fetch ^(9,10) = ^ABC(1,5,7,9,10)
; 4. store ^(3,4) = ^ABC(1,5,7,9,3,4)
; naked indicator is now: ^ABC(1,5,7,9,3,

$Piece(VALUE,STRING,FROM,TO)
Set ^ABC(1,2)="reset naked indicator"
; naked indicator is now ^ABC(1,
Set ^(3,4)=$Piece(^(5,6),^(7,8),^(9,10),^(11,12))
; 1. fetch ^(5,6) = ^ABC(1,5,6)
; 2. fetch ^(7,8) = ^ABC(1,5,7,8)
; 3. fetch ^(9,10) = ^ABC(1,5,7,9,10)
; 4. fetch ^(11,12) = ^ABC(1,5,7,9,11,12)
; 5. store ^(3,4) = ^ABC(1,5,7,9,11,3,4)
; naked indicator is now: ^ABC(1,5,7,9,11,3,

Set $Piece(VALUE,STRING,FROM,TO)=VALUE
Set ^ABC(1,2)="reset naked indicator"
; naked indicator is now ^ABC(1,
Set $Piece(^(3,4),^(5,6),^(7,8),^(9,10))=^(11,12)
; 1. fetch ^(5,6) = ^ABC(1,5,6)
; 2. fetch ^(7,8) = ^ABC(1,5,7,8)
; 3. fetch ^(9,10) = ^ABC(1,5,7,9,10)
; 4. fetch ^(11,12) = ^ABC(1,5,7,9,11,12)
; 5. if ^ABC(1,5,7,9,10) < ^ABC(1,5,7,8) or
; if ^ABC(1,5,7,9,10) < 1
; don’t store, naked indicator is ^ABC(1,5,7,9,11,
; else continue
; 6. fetch/store ^(3,4) = ^ABC(1,5,7,9,11,3,4)
; naked indicator is now: ^ABC(1,5,7,9,11,3,

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Copyright © Standard Documents; 1977-2024 MUMPS Development Committee;
Copyright © Examples: 1995-2024 Ed de Moel;
Copyright © Annotations: 2003-2008 Jacquard Systems Research
Copyright © Annotations: 2008-2024 Ed de Moel.

The information in this page is NOT authoritative and subject to be modified at any moment.
Please consult the appropriate (draft) language standard for an authoritative definition.

Some specifications are "approved for inclusion in a future standard". Note that the MUMPS Development Committee cannot guarantee that such future standards will indeed be published.

This page most recently updated on 15-Nov-2023, 13:11:13.

For comments, contact Ed de Moel (demoel@jacquardsystems.com)