testlist <- list(at = c(3.46307333081151e+154, -1.25006575434783e+282, 5.14315958723004e-160,  -1.08982851244395e-91, 2.26028581282016e-121, 2.90187404801145e-218,  5.02377921017453e+68, 2.75658669115993e-140, -2.12146658863353e-129,  7.03950133407821e+182, 3.11486979596129e-278, -1.80101653971272e+304,  1.12532219283171e+115, 5.73789315064701e-176, 1.10806737892218e+68,  -5.4883237864464e-299, -2.46215825142752e+95, -2.19156402442896e-61,  -4.11438079365031e-171, 8.57534627909826e+102, 4.32456964455111e+28,  -6.06081306736851e+255, -5.05165404097533e-11, -2.42564334960225e-09,  -1.78254019397664e-50, 7.92240872417722e-30, 4.70841294054683e+275,  5.6011403791765e+146, 4.43545761288614e+194, 1.39904849951932e+104,  -4.63149211013217e+27, -1.13120870512348e-79, -3.82241137873727e+242,  3.08364931258482e-49, 1.44605238901045e-83, 2.90683153640099e-303,  7.48291660915237e-118, -2.8961868307543e-251, 3.50654001945524e+269,  2.80744354667388e+21, 1.11090134439184e+76, 4.88550811687313e-175,  -2.56145938987172e+174, -1.47196836631238e-263, 2.40496213255775e+95,  -4.53220759914675e+237, -13695006786346297344, -2.83250127448473e+50,  -9.57755823478287e-238, 6.50328479036949e-259, 8.7622985532251e+306,  1.86782215155163e+23, -1.50101214956229e-158, -5.25074613121717e+275,  3.987001965522e+79, -2.86116214733671e+159, -2.7469251900993e-60,  2.00767920396136e-104, -1.72732802217387e+100, 2.73480986495337e-174,  -2.55994490342304e-197), ease = c(NA, "mnofdghdfdhvczrjhhyl",  "otxwgumbxzkfceyuthck", "baarsnomdkwdclpvm", "ggbyfayybmjz",  "kiscuedctacrjfranaqf", "hcncpfnwprndbipzvwhv", "jolui", NA,  "cfcghckvsk", "qdjwohyvmiixtbazapdn", "uryehqewumxxjrdxlzre",  "dcbofefnh", NA, "prkpqyncj", "vajteqqltmtptnztmqfz", "oldtqvahjdyjofjfqwxy",  NA, "kpxroalmpnokgnjfbqyp", NA, "zixbjxnzdcacczqqmavn", NA, NA,  "rxdhyaovwoxyzozo", NA, NA, "ufxqcikdhyfafdjecchk"), from = c(NA,  "fiewpwonjdmvmrsuttzw", NA, "ykxyulqqcgbvhtyehneo", NA, "eizvbymlxpgmaxalcotw",  NA, NA, "l", "vwag", "kryb", "grriywikxyphlzjld", "plkaml", NA,  "ijmftkktdemallvjo", NA, "hdquxo", "uuvnqvilw", "pdxv", "yqdznuj",  NA, "runkiurqmtvhpyjoeld", NA, NA, "xsjqnsegzdznmyjruruo", NA,  NA, "rwmbozcayazeaskmicms", "acsovvhpqvz", "rkihkhtbbb", NA,  "aiazjtwgkdhjdctbhsil", "bcmejfxybootpmzasdvt", NA, "worixwfwpytmwqehtofa",  NA, NA, NA, "asldqtvdloddatdlkagv", "rzebbhowkvjpmtkugfng", "kriiccwgejcdrstbfizf",  NA, NA, "hackmuyymgsxztmxibov", "irhmw", "kjqeroxocebwyzwoukzp",  NA, NA, "oklxosxloeqbzgfwnvtq", "vkhevuvitndjwnqjqkek", NA, "fouihuiddqegarcpqruc",  "koekfqgirpgaupdhsr", "oqrpajvggle", "zdomxp", "zwzkuqopedfesrcimmdr",  "dpsniytvopilsmizo", "fbnajovehdaclrtkitsw", "kylywkabpucqrmotqace",  NA, NA, NA, "tfjuzkacbkdidvrbzcph", NA, "gojl", NA, "gxsspcpvpqljpvyrklsc",  "ffkcbrbybdkyitmyakmw", NA, "wavxagdzxpullglwiyve", "ihxkdxwruahiguqkyvtl",  NA, "qqcwtdlmom", NA, NA, NA, "fduagwfpqojauwcjojdm", "pprqwwyfewggkfods",  NA, "yohmypjqdmzavahqer", "gquiwkughlbdaffdrtgt", "ozccxbeojiigshorjuwm",  "ezyfljpqlcpyfirrgvjf", NA, ""), to = c(NA, "uxfrjyjnevhndbtimvdx",  "bbu", "kpmqsibuqtfbrsuormdv", "xcpmvrafulfzgvqufq", "tpjrkervsbzayfwypzzh",  "deyjkmxmmztqrotxfraz", NA, "mtkrtvcodxuzjeeghwsp", NA))
result <- do.call(tweenr:::constant_at_interpolator,testlist)
str(result)