Opened 11 years ago

# Adding a "swap" method to equation objects.

Reported by: Owned by: Joal Heagney minor sage-6.4 symbolics swap, left hand side, right hand side, inequalities Ivan Andrus, Joal Heagney N/A

### Description

Often when working with sage equations, it's desirable to swap the left and right hand side of the equations. (Makes substitutions easier for a start, allows manual solving of inequalities, etc.)

A model implementation by Ivan Andrus https://groups.google.com/forum/#!topic/sage-support/lKbMSQrFhGg (in function form) is supplied below (with some rearrangement so equal operator case is tested first):

```import operator
def reverse_inequality(eq):
"""
Reverse the order of the inequality without changing it's meaning.
"""
orig_op = eq.operator() # The "top-level" operator
if orig_op == operator.eq:
op = operator.eq
elif orig_op == operator.lt:
op = operator.gt
elif orig_op == operator.le:
op = operator.ge
elif orig_op == operator.gt:
op = operator.lt
elif orig_op == operator.ge:
op = operator.le
elif orig_op == operator.ne:
op = operator.ne
else:
raise TypeError, "this expression must be a relation"
return op(eq.rhs(), eq.lhs())
```

My request is that something similar be attached to equation objects as a method.

### comment:1 Changed 11 years ago by Joal Heagney

Authors: → Ivan Andrus, Joal Heagney

### comment:2 Changed 9 years ago by Jeroen Demeyer

Milestone: sage-5.11 → sage-5.12

### comment:3 Changed 9 years ago by For batch modifications

Milestone: sage-6.1 → sage-6.2

### comment:4 Changed 9 years ago by For batch modifications

Milestone: sage-6.2 → sage-6.3

### comment:5 Changed 8 years ago by For batch modifications

Milestone: sage-6.3 → sage-6.4

### comment:6 Changed 8 years ago by Ralf Stephan

Component: algebra → symbolics changed from Alex Ghitza to Burcin Erocal

### comment:7 Changed 8 years ago by Ralf Stephan

Owner: Burcin Erocal deleted
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