1 | initial version |

I agree that `f.subs(a == 3)`

is bad syntax and should probably be deprecated. For substitutions, it is much clearer to use a Python dictionary:

```
sage: a, b = var('a b')
sage: f = a*x + b
sage: f.subs({a: 3, b: -2})
3*x - 2
```

2 | No.2 Revision |

I agree that `f.subs(a == 3)`

is bad syntax and should probably be deprecated. For substitutions, it is much clearer to use a Python dictionary:

```
sage: a, b = var('a b')
sage: f = a*x + b
sage: f.subs({a: 3})
b + 3*x
sage: f.subs({a: 3, b: -2})
3*x - 2
```

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