# Is the version not upward compatible？

**URL:** <https://alloytools.discourse.group/t/is-the-version-not-upward-compatible/245>\
**Category:** Uncategorized\
**Created:** [March 18, 2022, 6:15pm UTC](https://alloytools.discourse.group/t/is-the-version-not-upward-compatible/245 "2022-03-18T18:15:17Z")\
**Posts on this page:** 1\
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**Author:** ![grayswandyr](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/grayswandyr/32/17_2.png) [@grayswandyr](https://alloytools.discourse.group/u/grayswandyr)\
**Post date:** [March 18, 2022, 6:19pm UTC](https://alloytools.discourse.group/t/is-the-version-not-upward-compatible/245/2 "2022-03-18T18:19:43Z")

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Please copy paste your model target than showing a screenshot, it will be easier for people to test it. Here the issue may be due to the presence of the prime symbol as macro arguments. In general I would advise against using macros as much as you can. There are also issues with the way you update days, I suggest you refer to [this post](https://alloytools.discourse.group/t/alloytools-models-algorithms-echo/223) for a nice example of the canonical way to write models.

EDIT: notice that in Alloy 6, the prime symbol cannot be used for identifiers anymore, the prime symbol now denotes the value of the variable in the next instant. We have an on-going book about Alloy 6 [here](https://haslab.github.io/formal-software-design/).

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