# 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:

add a comment

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 -0600
**

Seen: **127 times**

Last updated: **Jan 02 '12**

Substitute formal function by an expression in a differential equation

Substitution of a list of variables

Substituting a particular value for a parameter

automatic substitution within functions?

Is applying a ring homomorphism faster than symbolic substitution?

Substituting function value in an expression

Defining and manipulating vector equations with cross and dot products

Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.