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author | Kaz Kylheku <kaz@kylheku.com> | 2014-02-10 01:40:46 -0800 |
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committer | Kaz Kylheku <kaz@kylheku.com> | 2014-02-10 01:40:46 -0800 |
commit | 7be3f9c4b4453a6ae7d9ba0f17953b3777baa4b1 (patch) | |
tree | b501f3af3bc16befeefb6278fbbc51a69577210c /eval.c | |
parent | 9791175d2bb5175aa54379000bf19caf9b34a188 (diff) | |
download | txr-7be3f9c4b4453a6ae7d9ba0f17953b3777baa4b1.tar.gz txr-7be3f9c4b4453a6ae7d9ba0f17953b3777baa4b1.tar.bz2 txr-7be3f9c4b4453a6ae7d9ba0f17953b3777baa4b1.zip |
* eval.c (rperm, perm_str): Just in case, return a mutable empty
string, rather than null_string, which is a literal.
(k_conses, comb_while_fun, comb_gen_fun_common,
comb_list_gen_fun, comb_list, comb_vec_gen_fun, comb_vec,
comb_str_gen_fun, comb_str, comb): New static functions.
(eval_init): Registered comb as instrinsic.
* txr.1: Documented comb.
Diffstat (limited to 'eval.c')
-rw-r--r-- | eval.c | 137 |
1 files changed, 135 insertions, 2 deletions
@@ -2217,7 +2217,7 @@ static val rperm(val seq, val k) case LSTR: case LIT: if (zerop(k)) - return cons(null_string, nil); + return cons(string(L""), nil); return rperm_str(seq, k); default: type_mismatch(lit("rperm: ~s is not a sequence"), seq, nao); @@ -2377,7 +2377,7 @@ static val perm_str(val p, val k) k = default_arg(k, length_str(p)); if (k == zero) { - return cons(null_string, nil); + return cons(string(L""), nil); } else { val state = perm_init_common(vector_list(list_str(p)), k); return generate(func_f0(state, perm_while_fun), @@ -2414,6 +2414,138 @@ static val perm(val seq, val k) } } +static val k_conses(val list, val k) +{ + val iter = list, i = k; + list_collect_decl (out, ptail); + + for (; consp(iter) && gt(i, zero); iter = cdr(iter), i = minus(i, one)) + ptail = list_collect(ptail, iter); + + if (i != zero) + uw_throwf(numeric_error_s, + lit("comb: permutation length ~s exceeds sequence length ~s"), + k, length(list), nao); + + return out; +} + +static val comb_while_fun(val state) +{ + return car(state); +} + +static void comb_gen_fun_common(val state) +{ + val iter; + val prev = nil; + + for (iter = state; consp(iter); iter = cdr(iter)) { + val curr = first(iter); + val curr_rest = rest(curr); + if (curr_rest != prev && consp(curr_rest)) { + *car_l(iter) = curr_rest; + return; + } else if (rest(iter)) { + val next = second(iter); + val next_rest = rest(next); + val next_rest_rest = rest(next_rest); + prev = curr; + if (next_rest != curr && consp(next_rest_rest)) + prev = *car_l(iter) = next_rest_rest; + } + } + + *car_l(state) = nil; +} + +static val comb_list_gen_fun(val state) +{ + val out = nreverse(mapcar(car_f, state)); + comb_gen_fun_common(state); + return out; +} + +static val comb_list(val list, val k) +{ + val state = nreverse(k_conses(list, k)); + return generate(func_f0(state, comb_while_fun), + func_f0(state, comb_list_gen_fun)); +} + +static val comb_vec_gen_fun(val state) +{ + val nn = length_list(state); + cnum i, n = c_num(nn); + val iter, out = vector(nn, nil); + + for (iter = state, i = n - 1; i >= 0; iter = cdr(iter), i--) + out->v.vec[i] = car(car(iter)); + + comb_gen_fun_common(state); + return out; +} + +static val comb_vec(val vec, val k) +{ + val state = nreverse(k_conses(list_vector(vec), k)); + return generate(func_f0(state, comb_while_fun), + func_f0(state, comb_vec_gen_fun)); +} + +static val comb_str_gen_fun(val state) +{ + val nn = length_list(state); + cnum i, n = c_num(nn); + val iter, out = mkustring(nn); + + out->st.str[n] = 0; + + for (iter = state, i = n - 1; i >= 0; iter = cdr(iter), i--) + out->st.str[i] = c_chr(car(car(iter))); + + comb_gen_fun_common(state); + return out; +} + +static val comb_str(val str, val k) +{ + val state = nreverse(k_conses(list_str(str), k)); + return generate(func_f0(state, comb_while_fun), + func_f0(state, comb_str_gen_fun)); +} + +static val comb(val seq, val k) +{ + if (!integerp(k)) + type_mismatch(lit("comb: ~s is not an integer"), k, nao); + + if (lt(k, zero)) + uw_throwf(numeric_error_s, lit("comb: ~s is not a positive integer"), + k, nao); + + switch (type(seq)) { + case CONS: + case LCONS: + case NIL: + if (k == zero) + return cons(nil, nil); + return comb_list(seq, k); + case VEC: + if (k == zero) + return cons(vector(zero, nil), nil); + return comb_vec(seq, k); + case STR: + case LSTR: + case LIT: + if (k == zero) + return cons(string(L""), nil); + return comb_str(seq, k); + default: + type_mismatch(lit("comb: ~s is not a sequence"), seq, nao); + } +} + static val errno_wrap(val newval) { val oldval = num(errno); @@ -3008,6 +3140,7 @@ void eval_init(void) reg_fun(intern(lit("force"), user_package), func_n1(force)); reg_fun(intern(lit("rperm"), user_package), func_n2(rperm)); reg_fun(intern(lit("perm"), user_package), func_n2o(perm, 1)); + reg_fun(intern(lit("comb"), user_package), func_n2(comb)); reg_fun(throw_s, func_n1v(uw_throw)); reg_fun(intern(lit("throwf"), user_package), func_n2v(uw_throwfv)); |