# no method matching opsum on boson indices

**URL:** <https://itensor.discourse.group/t/no-method-matching-opsum-on-boson-indices/528>\
**Category:** ITensor Julia Questions\
**Created:** [November 23, 2022, 4:31pm UTC](https://itensor.discourse.group/t/no-method-matching-opsum-on-boson-indices/528 "2022-11-23T16:31:38Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![jake](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/jake/32/521_2.png) [@jake](https://itensor.discourse.group/u/jake)\
**Post date:** [November 23, 2022, 4:31pm UTC](https://itensor.discourse.group/t/no-method-matching-opsum-on-boson-indices/528/1 "2022-11-23T16:31:38Z")

</div>

I am new to ITensor so I apologize in advance if my question is trivial. I am toying around trying to do scalar field theory and am defining field operators on a set of boson sites of max occupation of d. I define several functions relevant to a scalar field theory.  
However, when I opsum phi2 over indices in sites, I get this error.

 ![image](https://global.discourse-cdn.com/free1/uploads/itensor/original/1X/4ab7379800f9f22744d6c4d0fcfc22b70663d23e.png)  
Which has me confused since my site type is defined as boson. What am I doing wrong.  
Thank you very much.

---

<div class="post-metadata">

**Author:** ![miles](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/miles/32/6_2.png) [@miles](https://itensor.discourse.group/u/miles)\
**Post date:** [November 23, 2022, 4:46pm UTC](https://itensor.discourse.group/t/no-method-matching-opsum-on-boson-indices/528/2 "2022-11-23T16:46:56Z")

</div>

Hi Jake, it’s a good question. I think the issue may be that Julia doesn’t overload functions unless you “import” them first. Or you can put the module name in front of the function (`ITensors.`) to tell Julia it’s an overload.

So please try writing the names of the functions as

```auto
function ITensors.op(…)

```

to see if that allows Julia to find your overloads.