# subs_expr with e^t

Is there a reason why subs_expr() won't work here?

sage: version() 'Sage Version 4.7.2, Release Date: 2011-10-29' sage: t = var('t') sage: foo = e^t sage: foo.subs_expr(e==e.n()) e^t sage:

subs_expr with e^t

Is there a reason why subs_expr() won't work here?

sage: version() 'Sage Version 4.7.2, Release Date: 2011-10-29' sage: t = var('t') sage: foo = e^t sage: foo.subs_expr(e==e.n()) e^t sage:

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5

Use a wild card (a variable that matches everything) to do complicated subs_expr. I would suggest this technique to be written in sage tutorials. It is very useful to me.

```
sage: t = var('t')
sage: foo = e^t
sage: w0 = SR.wild(0)
sage: foo.subs_expr(e^w0==e.n()^w0)
2.71828182845905^t
```

1

Asked: **
2012-01-01 17:13:51 -0500
**

Seen: **144 times**

Last updated: **Jan 02 '12**

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