---
sympy/physics/secondquant.py | 29 ++++++++++++++++++++---------
1 files changed, 20 insertions(+), 9 deletions(-)
diff --git a/sympy/physics/secondquant.py b/sympy/physics/secondquant.py
index 93f9ca3..858c222 100644
--- a/sympy/physics/secondquant.py
+++ b/sympy/physics/secondquant.py
@@ -2505,27 +2505,38 @@ def _substitute(expr, ordered_dummies, arg_iterator,
**require):
Dummies without the keyword in .assumptions0 will be default to
give the value False.
+ Warning
+ =======
+
+ Apart from checking the keyword requirements, nothing is done to prevent
+ loss of information during substitution.
+
+
+ Examples
+ ========
+
>>> from sympy import Symbol
- >>> from sympy.physics.secondquant import substitute_dummies, _substitute
+ >>> from sympy.physics.secondquant import substitute_dummies, _substitute,F
>>> q = Symbol('q', dummy=True)
>>> i = Symbol('i', below_fermi=True, dummy=True)
>>> a = Symbol('a', above_fermi=True, dummy=True)
-
>>> reverse = lambda x: reversed(x)
- >>> _substitute(a, [q], reverse, above_fermi=True) # will succeed
- _a
- >>> _substitute(i, [q], reverse, above_fermi=True) # will not succeed
- _i
- >>> _substitute(i, [q], reverse, above_fermi=False) # will succeed
- _i
+
+ >>> _substitute(F(a), [q], reverse, above_fermi=True) # will succeed
+ AnnihilateFermion(_q)
+ >>> _substitute(F(i), [q], reverse, above_fermi=True) # will not succeed
+ AnnihilateFermion(_i)
+ >>> _substitute(F(i), [q], reverse, above_fermi=False) # will succeed
+ AnnihilateFermion(_q)
With no keywords, all dummies are substituted.
+ >>> _substitute(F(i), [q], reverse) # will succeed
+ AnnihilateFermion(_q)
"""
dummies = _remove_duplicates(_get_dummies(expr, arg_iterator, **require))
subslist = _get_subslist(dummies, ordered_dummies)
-
result = expr.subs(subslist)
return result
--
1.6.5
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