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Left Hand Pointer

IF

M[UMPS] by Example

Right Hand Pointer

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

If A=5 Set B=3 Write "..."
The most common method to make several actions dependent on one test.

If (A>5)&(A<16) Write "6 ≤ value ≤ 15"
If A>5 If A<16 Write "6 ≤ value ≤ 15"
If A>5,A<16 Write "6 ≤ value ≤ 15"

The above three lines have practically the same effect. All three test whether or not the value of a local variable is between two values, and write a message if this is the case. In the first example, however, the test A<16 is also evaluated when A<5, whereas in the other two cases, because the first IF command on the line was unsuccessful, the rest of the line was already being skipped.
There is no difference between the second and third line, other than that the third line is more compact.

The advantage of not evaluating expressions if an earlier test in the same line yielded a false result may become obvious in cases like:
If X=3,^|"FARAWAY"|GLOBAL(1,2,3) Do ACTION
By putting the 'simple' test at the beginning of the line, transactions across the network may be prevented in those cases where there is no need to execute them.

Examples with naked references:

If VALUE
Set ^ABC(1,2)="reset naked indicator"
; naked indicator is now ^ABC(1,
If ^(3,4)
; naked indicator is now: ^ABC(1,3,
; Actual reference is: ^ABC(1,3,4)

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Copyright © Standard Documents; 1977-2017 MUMPS Development Committee;
Copyright © Examples: 1995-2017 Ed de Moel;
Copyright © Annotations: 2003-2017 Jacquard Systems Research.

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 13-Sep-2014, 10:09:43 .

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