pystencils.sympyextensions.math.replace_second_order_products

pystencils.sympyextensions.math.replace_second_order_products#

pystencils.sympyextensions.math.replace_second_order_products(expr, search_symbols, positive=None, replace_mixed=None)#

Replaces second order mixed terms like 4*x*y by 2*( (x+y)**2 - x**2 - y**2 ).

This makes the term longer - simplify usually is undoing these - however this transformation can be done to find more common sub-expressions

Parameters:

  • expr (Expr) – input expression

  • search_symbols (Iterable[Symbol]) – symbols that are searched for for example, given [x,y,z] terms like x*y, x*z, z*y are replaced

  • positive (Optional[bool]) – there are two ways to do this substitution, either with term (x+y)**2 or (x-y)**2 . if positive=True the first version is done, if positive=False the second version is done, if positive=None the sign is determined by the sign of the mixed term that is replaced

  • replace_mixed (Optional[List[Assignment]]) – if a list is passed here, the expr x+y or x-y is replaced by a special new symbol and the replacement equation is added to the list

Return type:

Expr

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