bolligerallstar

this is neverending confusing story

int in your example is rate quoted as quarterly p.a.
in this case you divide the rate by number of periods (here quarters) to get to holding period rate

inf is "quoted" (calculated) as annual rate therefore the compouding ^

you can ask why not devide inf by 4 as int?
the reason is here
1+inf = ((1 + infl)^(3/12))^12/3
1+infl not equal to (1+inf/4)^4

but int is in this case quoted so that if you wanted to know int over whole year you need to calc:
(1+int/4)^4 because there is nothing like 1+int, the int is paid quaryerly

bond equivalent yield uses the same logic - semiannual rate

this is my best explanation