Name

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KDM_ISDEFINED

Purpose

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  This procedure checks if a variable is defined or not, and
  optionally sets it to a default value, or prompts the user to
  enter a value.
  This is a fancy wrapper for N_ELEMENTS() EQ 0 and KEYWORD_SET()

Category

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Genaral Programming

Calling Sequence

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  KDM_ISDEFINED, Variable

Inputs

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  Variable: A variable that may or may not be defined.

Keyword Parameters

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  DEFAULT: The value to set the variable to. This is ONLY if
            the variable is not defined.
  PROMPT: The prompt to use to let the user set the value. The user
          is only prompted to enter a value if the variable is
          undefined.

Outputs

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  Variable may be changed. If it was undefined, and one (or both) of
  the DEFAULT and/or PROMPT keywords were set.

Restrictions

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  If the input variable is undefined, and no default value is
  supplied, but a PROMPT value is supplied, then the returned
  variable is of type STRING because that is the most general data
  type.

Example

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  If a variable is defined, nothing happens:
  x = 42
  kdm_isdefined, x, default='foo', prompt='P'
  Set an undefined variable to a default value:
  kdm_isdefined, xx, default='bar'
  kdm_isdefined, xx2, default=dist(42,24)
  kdm_isdefined, ll, d=[0.,0], p="Enter lat,lon: "
  Set an undefined variable to user inputs:
  kdm_isdefined, xxx, prompt='Enter Something: '
  Set an undefinde variable to a user input but control the type:
  kdm_isdefined, xxxx, prompt='Enter Something: ', default=BYTE(42)

Modification History

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  Written by: Ken Mankoff, 2010-03
              2010-04-18: Provide type hint. Allow empty strings to
                          default to default input if supplied.