118 #ifndef PROM_INCLUDED   119 #define PROM_INCLUDED   128 #include "prom_linked_list.h"   129 #include "prom_map.h"   134 #endif //  PROM_INCLUDED https://prometheus.io/docs/concepts/metric_types/#gauge 
A Prometheus collector returns a collection of metrics. 
https://prometheus.io/docs/concepts/metric_types/#histogram 
Functions for interfacting with metric samples directly. 
https://prometheus.io/docs/concepts/metric_types/#counter 
Functions for interacting with histogram metric samples directly. 
Functions for retrieving metric samples from metrics given an ordered set of labels. 
The collector registry registers collectors for metric exposition. 
https://prometheus.io/docs/concepts/metric_types/#histogram