Expands relative filename to first available one in path.
DESCRIPTION
When given an absolute filename, (e.g. on Linux/Unix one starting with a slash
or tilde), this function returns it unchanged. Otherwise it tries to find the
file in one of the directories in the path argument. An initial dollar sign $
in each path is interpreted as a reference to the current setting of hol_dir.
To get an actual $ at the start of the filename, actually use two dollar
signs $$.
FAILURE CONDITIONS
Fails if no file is found on the path.
EXAMPLE
# file_on_path (!load_path) "Library/analysis.ml";;
val it : string = "/home/johnh/holl/Library/analysis.ml"
# file_on_path (!load_path) "Library/wibble.ml";;
Exception: Not_found.