Persian onager the Asiatic wild ass is known simply as onager, it now also serves as the Persian wild ass's scientific name, as well ("Equus hemionus onager"). Information on the basic biology of the subspecies and how it differs from others is lacking, which hampers conservation efforts. Onagers used to be numerous from the Middle East to China. However, until the 19th century, their population has been reduced from several thousand to a few thousand. Currently, more than 600 Persian onagers are living in the wild. Persian wild asses are known to inhabit mountain steppes, semidesert, or desert plains. They are usually
Type system or an "effect system", which enables even more program specifications to be verified by a type checker. Beyond simple value-type pairs, a virtual "region" of code is associated with an "effect" component describing "what" is being done "with what", and enabling for example to "throw" an error report. Thus the symbolic system may be a "type and effect system", which endows it with more safety checking than type checking alone. Whether automated by the compiler or specified by a programmer, a type system makes program behavior illegal if outside the type-system rules. Advantages provided by programmer-specified type systems include: Advantages