diff options
| -rw-r--r-- | arith.c | 13 | ||||
| -rw-r--r-- | arith.h | 1 | ||||
| -rw-r--r-- | txr.1 | 32 |
3 files changed, 46 insertions, 0 deletions
@@ -192,6 +192,18 @@ val unum(ucnum u) } } +val bignum_len(val num) +{ + switch (type(num)) { + case CHR: case NUM: + return zero; + case BGNUM: + return unum(mp(num)->used); + default: + type_mismatch(lit("bignum-digits: ~s is not an integer"), num, nao); + } +} + int highest_bit(int_ptr_t n) { #if SIZEOF_PTR == 8 @@ -3089,6 +3101,7 @@ void arith_init(void) reg_varl(intern(lit("*e*"), user_package), flo(M_E)); reg_varl(intern(lit("%e%"), user_package), flo(M_E)); + reg_fun(intern(lit("bignum-len"), user_package), func_n1(bignum_len)); reg_fun(intern(lit("divides"), user_package), func_n2(divides)); reg_fun(intern(lit("bits"), system_package), func_n1(bits)); reg_fun(intern(lit("digpow"), user_package), func_n2o(digpow, 1)); @@ -36,6 +36,7 @@ val normalize(val bignum); val in_int_ptr_range(val bignum); ucnum c_unum(val num); val unum(ucnum u); +val bignum_len(val num); val cum_norm_dist(val x); val inv_cum_norm(val p); val n_choose_k(val n, val k); @@ -35650,6 +35650,38 @@ that value is then added to the result accumulator. (rpoly 10 '(1 2 3)) -> 321 .cble +.coNP Function @ bignum-len +.synb +.mets (bignum-len << arg ) +.syne +.desc +The +.code bignum-len +function reports the machine-specific +.I "bignum order" +of the integer or character argument +.metn arg . + +If +.meta arg +is a character or +.code fixnum +integer, the function returns zero. + +Otherwise +.meta arg +is expected to be a +.code bignum +integer, and the function returns the number of "limbs" used for its +representation, a positive integer. + +Note: the +.code bignum-len +function is intended to be of use in algorithms whose performance +benefits from ordering the operations on multiple integer operands +according to the magnitudes of those operands. The function provides an +estimate of magnitude which trades accuracy for efficiency. + .SS* Bit Operations In \*(TL, similarly to Common Lisp, bit operations on integers are based on a concept that might be called "infinite two's-complement". |