create ?options total creates a new progress bar tied to stdout. The bar reaches 100% when update is called with total.

reset t resets the current bar.

update t v sets the progress bar a value v, the proportion of the bar displayed is v / total where total is the value that has been used to initialize the bar. The bar is then displayed.

incr t ~by increases the current value stored in t by by.

close t finalizes the bar and prints a new line.

with_bar total ~f creates a new bar and runs f using it. close is called when f returns or if f raises.