The ifxptex package --- Detect pTeX and its derivatives CTAN Homepage: https://ctan.org/pkg/ifxptex Repository: https://github.com/Man-Ting-Fang/ifxptex Version: 2017-12-27 v0.2 Copyright 2017 Yue ZHANG License: Knuth License (https://ctan.org/license/knuth) This package provides commands for detecting pTeX and its derivatives (e-pTeX, upTeX, e-upTeX, and ApTeX). Both LaTeX and plain TeX are supported.