diff options
| -rw-r--r-- | arith.c | 64 | ||||
| -rw-r--r-- | lib.h | 1 | ||||
| -rw-r--r-- | txr.1 | 58 |
3 files changed, 122 insertions, 1 deletions
@@ -72,7 +72,7 @@ val sin_s, cos_s, tan_s, asin_s, acos_s, atan_s, atan2_s, r_atan2_s; val log_s, log2_s, log10_s, exp_s, sqrt_s; val logand_s, logior_s, logxor_s; val lognot1_s, lognot_s, r_lognot_s, logtrunc_s, r_logtrunc_s; -val sign_extend_s, ash_s, bit_s, width_s, logcount_s; +val sign_extend_s, ash_s, bit_s, width_s, bitset_s, logcount_s; val make_bignum(void) { @@ -3340,6 +3340,66 @@ val maskv(struct args *bits) return accum; } +val bitset(val n) +{ + val self = bitset_s; + list_collect_decl (out, ptail); + + switch (type(n)) { + case NUM: + case CHR: + { + cnum c = c_n(n); + ucnum d = c; + int p = 0; + + if (c < 0) + d = ~d; + + for (; d; d >>= 1, p++) + if (d & 1) + ptail = list_collect(ptail, num_fast(p)); + + return out; + } + case BGNUM: + { + mp_int *mn = mp(n); + + if (mp_cmp_z(mn) == MP_LT) { + mp_int tmp; + mp_size i = 0; + ucnum p = 0; + mp_2comp(mn, &tmp, mn->used); + for (; i < tmp.used; i++) { + mp_digit m; + mp_digit d = tmp.dp[i]; + for (m = 1; m; m <<= 1, p++) + if ((d & m) == 0) + ptail = list_collect(ptail, unum(p)); + } + mp_clear(&tmp); + } else { + mp_size i = 0; + ucnum p = 0; + for (; i < mn->used; i++) { + mp_digit m; + mp_digit d = mn->dp[i]; + for (m = 1; m; m <<= 1, p++) + if ((d & m) != 0) + ptail = list_collect(ptail, unum(p)); + } + } + + return out; + } + case COBJ: + return do_unary_method(self, self, n); + default: + uw_throwf(error_s, lit("~a: non-integral operand ~s"), self, n, nao); + } +} + val logcount(val n) { val self = logcount_s; @@ -4275,6 +4335,7 @@ void arith_init(void) ash_s = intern(lit("ash"), user_package); bit_s = intern(lit("bit"), user_package); width_s = intern(lit("width"), user_package); + bitset_s = intern(lit("bitset"), user_package); logcount_s = intern(lit("logcount"), user_package); if (opt_compat && opt_compat <= 199) { @@ -4373,6 +4434,7 @@ void arith_init(void) reg_fun(intern(lit("mask"), user_package), func_n0v(maskv)); reg_fun(width_s, func_n1(width)); reg_fun(logcount_s, func_n1(logcount)); + reg_fun(bitset_s, func_n1(bitset)); reg_fun(intern(lit("cum-norm-dist"), user_package), func_n1(cum_norm_dist)); reg_fun(intern(lit("inv-cum-norm"), user_package), func_n1(inv_cum_norm)); reg_fun(intern(lit("n-choose-k"), user_package), func_n2(n_choose_k)); @@ -796,6 +796,7 @@ val ash(val a, val bits); val bit(val a, val bit); val maskv(struct args *bits); val logcount(val n); +val bitset(val n); val string_own(wchar_t *str); val string(const wchar_t *str); val string_utf8(const char *str); @@ -38152,6 +38152,63 @@ In other words, the following equivalences hold: (mask a b c ...) <--> (logior (mask a) (mask b) (mask c) ...) .brev +.coNP Function @ bitset +.synb +.mets (bitset << integer ) +.syne +.desc +The +.code bitset +function returns a list of the positions of bits which have a value of +1 in a positive +.meta integer +argument, or the positions of bits which have a value of zero in a negative +.meta integer +argument. The positions are ordered from least to greatest. The least +significant bit has position zero. If +.meta integer +is zero, the empty list +.code nil +is returned. + +A negative integer is treated as an infinite bit two's complement +representation. + +The argument may be a character. + +If +.meta integer +.code x +is non-negative, the following equivalence holds: + +.verb + x <--> [apply mask (bitset x)] +.brev + +That is to say, the value of +.code x +may be reconstituted by applying the bit positions returned by +.code bitset +as arguments to the +.code mask +function. + +The value of a negative +.code x +may be reconstituted from its +.code bitset +as follows: + +.verb + x <--> (pred (- [apply mask (bitset x)])) +.brev + +also, more trivially, thus: + +.verb + x <--> (- [apply mask (bitset (- x))]) +.brev + .coNP Function @ width .synb .mets (width << integer *) @@ -38675,6 +38732,7 @@ which must be an integer. .um width .um logcount +.um bitset .SS* Exception Handling |