mekso ternary operator: extract digit from number; X2nd macrodigit/term of number/tuple X1 when X1 is expressed in base/basis X3.
X2 defaults to 0; it must always be an integer. For the purposes of this description, suppose temporarily that the base is decimal/ten; this is for simplicity - statements generalize to other bases. The zeroth digit (X2 = 0) is the singles digit; the first digit (X2 = 1) is the tens digit; the nth digit (for any integer n) is the digit which represents the multiple of 10n; the positive-last (X2 = ma'uro) digit is the most significant digit/figure in a finite number expressed in decimal; the negative-first (X2 = -1) is the one-tenths digit; the negative-last digit for a terminating expansion in decimal is the least significant digit/figure of the number when expressed in decimal. Only macrodigits are extracted; so, in Roman numeral notation, decimal 120 = CXX, and the second (or positive-last) digit is C (which equals 100). X1 may be expressed in any base but X3 forces a conversion to its own base for the purposes of this extraction; X1, X2, X3, and the result of the extraction may all be expressed in any base (independent of one another) and the default is assumed to be default of the cultural context for the math (according to the CLL, this is usually decimal), explicitly differing from this base requires ju'u or similar (which is allowed). The result/output of this function is a digit (thus, it concatenates with other PA automatically) and must filter through the interpretation rules in order to be considered a number; unless it explicitly expressed otherwise, it is assumed to be in the base of whatever digit-string it occurs in or, failing this/being alone, the base used in the cultural context of the text - it is not necessarily expressed in base-X3.