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7.7.17.0. dmodoublext
Procedure from library nchomolog.lib (see nchomolog_lib).
- Usage:
- dmodoublext(M [,i]); M module, i optional int
- Compute:
- a presentation of Ext^i(Ext^i(M,D),D) for basering D
- Return:
- left module
- Note:
- by default, i is set to the integer part of the half of number of variables of D
for holonomic modules over Weyl algebra, the double ext is known to be holonomic left module
Example:
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