By default, the current directory is searched first, then the standard library directory. Directories added with -I are searched after the current directory, but before the standard library directory. When an unknown language is specified, or no translation is available for a message, American English is used by default. Operations from the cautious set perform range and bound checking on string and vector operations, as well as various sanity checks on their arguments. Programs compiled with -O fast are therefore slightly faster, but unsafe.
Compilation starts in an almost empty environment.
This option is not of general use. The default compilation mode is -O cautious . See chapter 14 for a complete listing of the modules in the cautious and fast sets. The standard library module toplevel , opened by default when the toplevel system is launched, provides a number of functions that control the toplevel behavior, load files in memory, and trace program execution. The .ml extension is automatically added to the file name, if not present.