# Strange behviour when trying to integrate gaussian function. bug?

I was trying integrate the following function

```
y=var('y')
integrate(x*exp(-(x-y)*(x-y)*2.0),x)
```

$$\frac{1}{8} \, {\left(\frac{2 \, {\left(\text{erf}\left(\sqrt{2} \sqrt{{\left(x - y\right)}^{2}}\right) - 1\right)} {\left(x - y\right)} \sqrt{\pi} y}{\sqrt{{\left(x - y\right)}^{2}}} - \sqrt{2} e^{\left(-2 \, {\left(x - y\right)}^{2}\right)}\right)} \sqrt{2}$$ The integral can easily be done by redefining variables and does not have to be expressed in terms of error functions. Also the behavior of sage becomes even strange when I change the coefficient from 2.0 to 2.1. Sage just refuses to do the integral

```
integrate(x*exp(-(x-y)*(x-y)*2.1),x)
```

$$\int x e^{\left(-2.1 \, {\left(x - y\right)}^{2}\right)}\,{d x}$$

Any ideas on how to make sage give an answer in the usual exponential form?

Edit: Sorry. My bad. It is an error function. However, I expect error function even for the second example, when I replace 2 by 2.1. Any ideas why that is the case?

Could you be specific about the transformation you have in mind? As usual, I'm missing something-- I can't see how to do it without an erf popping up. (And you should expect this comment to vanish after I realize how stupid I was. :^)

@DSM - no need to make comments vanish, that's part of the open development process, to keep a record of everyone's thoughts. "Stupid" comments may later turn out to be prescient.