# MethodError: no method matching isless(::Int64, ::AffExpr)

**URL:** <https://discourse.julialang.org/t/methoderror-no-method-matching-isless-int64-affexpr/69731>\
**Category:** Optimization (Mathematical)\
**Tags:** question, jump\
**Created:** [October 14, 2021, 6:39am UTC](https://discourse.julialang.org/t/methoderror-no-method-matching-isless-int64-affexpr/69731 "2021-10-14T06:39:36Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![vinicius\_de\_lima](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vinicius_de_lima/32/28717_2.png) [@vinicius\_de\_lima](https://discourse.julialang.org/u/vinicius_de_lima)\
**Post date:** [October 14, 2021, 10:27pm UTC](https://discourse.julialang.org/t/methoderror-no-method-matching-isless-int64-affexpr/69731/2 "2021-10-14T22:27:29Z")

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Please see [this link](https://discourse.julialang.org/t/problem-using-jump-with-user-defined-function/68835), I believe that you have to register the function `max` before using it in a model.

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