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Command Argument Indirection

Draft MDC Standard

8.1.3 Command argument indirection

Indirection is available for evaluation of either individual command arguments or contiguous sublists of command arguments. The opportunities for indirection are shown in the syntax definitions accompanying the command descriptions.

Typically, where a commandword carries an argument list, as in

   commandword SP L argument

the argument syntax will be expressed as

    argument::=

individual argument syntax
@ expratom V L argument


This formulation expresses the following properties of argument indirection.

  1. Argument indirection may be used recursively.
  2. A single instance of argument indirection may evaluate to one complete argument or to a sublist of complete arguments.

Unless the opposite is explicitly stated, the text of each command specification describes the arguments after all indirection has been evaluated.

Unless expressed otherwise, if individual argument syntax allows the @ expratom contruct, then argument indirection has precedence, i.e., the restriction on the value of expratom comes from the V operator of the argument indirection, not any other type of indirection.

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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.

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 14-Nov-2023, 21:35:19.

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