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Testing symbols

With the !ifset command you can test if a symbol was set in the preamble or via command line. The !ifnset tests if a symbol is not set.

As you know you can set symbols via command line by using the option -D and by the command !set.

The following example shows how to test the symbol `UseColour' and to display the right image:

!ifset [UseColor]
!image colour/tiger
!else
!image mono/tiger
!endif

If you call UDO with passing the option -D UseColor or if you set the symbol with !set UseColor inside the preamble UDO will display the color image instead of the monochrome image.


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Last updated on November 5, 2006

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