```\nfunction wln(int256 x) internal pure returns (int256) {\n    require(x > 0, "logE of negative number");\n    require(x <= 10000000000000000000000000000000000000000, "logE only accepts v <= 1e22 \* 1e18"); // in order to prevent using safe-math\n    int256 r = 0;\n    uint8 extra\_digits = longer\_digits - fixed\_digits;\n```\n