Add Array#to_h

mrbgems/mruby-array-ext/src/array.c

@@ -2,6 +2,7 @@
 #include "mruby/value.h"
 #include "mruby/array.h"
 #include "mruby/range.h"
+#include "mruby/hash.h"
 
 /*
  *  call-seq:
@@ -105,6 +106,48 @@ mrb_ary_values_at(mrb_state *mrb, mrb_value self)
   return mrb_get_values_at(mrb, self, RARRAY_LEN(self), argc, argv, mrb_ary_ref);
 }
 
+/*
+ *  call-seq:
+ *     ary.to_h   ->   Hash
+ *
+ *  Returns the result of interpreting <i>aray</i> as an array of
+ *  <tt>[key, value]</tt> paris.
+ *
+ *     [[:foo, :bar], [1, 2]].to_h
+ *       # => {:foo => :bar, 1 => 2}
+ */
+
+static mrb_value
+mrb_ary_to_h(mrb_state *mrb, mrb_value ary)
+{
+  mrb_int i;
+  mrb_value v, hash;
+
+  hash = mrb_hash_new_capa(mrb, 0);
+
+  for (i = 0; i < RARRAY_LEN(ary); ++i) {
+    v = mrb_check_array_type(mrb, RARRAY_PTR(ary)[i]);
+
+    if (mrb_nil_p(v)) {
+      mrb_raisef(mrb, E_TYPE_ERROR, "wrong element type %S at %S (expected array)",
+        mrb_str_new_cstr(mrb,  mrb_obj_classname(mrb, RARRAY_PTR(ary)[i])),
+        mrb_fixnum_value(i)
+      );
+    }
+
+    if (RARRAY_LEN(v) != 2) {
+      mrb_raisef(mrb, E_ARGUMENT_ERROR, "wrong array length at %S (expected 2, was %S)",
+        mrb_fixnum_value(i),
+        mrb_fixnum_value(RARRAY_LEN(v))
+      );
+    }
+
+    mrb_hash_set(mrb, hash, RARRAY_PTR(v)[0], RARRAY_PTR(v)[1]);
+  }
+
+  return hash;
+}
+
 void
 mrb_mruby_array_ext_gem_init(mrb_state* mrb)
 {
@@ -114,6 +157,7 @@ mrb_mruby_array_ext_gem_init(mrb_state* mrb)
   mrb_define_method(mrb, a, "at",     mrb_ary_at,     MRB_ARGS_REQ(1));
   mrb_define_method(mrb, a, "rassoc", mrb_ary_rassoc, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, a, "values_at", mrb_ary_values_at, MRB_ARGS_ANY());
+  mrb_define_method(mrb, a, "to_h",   mrb_ary_to_h, MRB_ARGS_REQ(0));
 }
 
 void

mrbgems/mruby-array-ext/test/array.rb

@@ -285,3 +285,11 @@ assert('Array#values_at') do
   assert_equal ['none', nil, nil, 'red', 'green', 'purple'], a.values_at(4..6, 0...3)
   assert_raise(TypeError) { a.values_at 'tt' }
 end
+
+assert('Array#to_h') do
+  assert_equal({}, [].to_h)
+  assert_equal({a: 1, b:2}, [[:a, 1], [:b, 2]].to_h)
+
+  assert_raise(TypeError)     { [1].to_h }
+  assert_raise(ArgumentError) { [[1]].to_h }
+end