Those literals are assigned then compared somewhere else in the code. When those literals are carrying a state, it is recommended to assign them to a constant, to ensure that both parts of the application use the same values..
| Literal | Assignations | Comparisons | 
| 200 | 
 | 
 | 
| 1000 | 
 | 
 | 
| on | 
 | 
 | 
| off | 
 | 
 | 
| trash | 
 | 
 | 
| -1 | 
 | 
 | 
| text | 
 | 
 | 
| url | 
 | 
 | 
| noindex | 
 | 
 | 
| utf-8 | 
 | 
 | 
| 1 | 
 | 
 | 
| full | 
 | 
 | 
| publish | 
 | 
 | 
| tracking | 
 | 
 | 
| post_tag | 
 | 
 | 
| none | 
 | 
 | 
| 0 | 
 | 
 | 
| / | 
 | 
 | 
| set-by-user | 
 | 
 | 
| home-page | 
 | 
 | 
| default | 
 | 
 | 
| imported | 
 | 
 | 
| tag | 
 | 
 | 
| post | 
 | 
 | 
| category | 
 | 
 | 
| term | 
 | 
 | 
| system-page | 
 | 
 | 
| post-type-archive | 
 | 
 | 
| user | 
 | 
 | 
| unindexed | 
 | 
 | 
| description | 
 | 
 | 
| error | 
 | 
 | 
| updated | 
 | 
 | 
| collectionpage | 
 | 
 | 
| wpseo_manage_options | 
 | 
 | 
| index | 
 | 
 |