Oh, and for 7-segment decoding specifically, you can also use an EEPROM as a cheeky decoder: input bits as the address, output value is the drive signals for the display.
But it's also starting to get tricky to find EEPROMs with parallel I/O, everthing's SPI these days to feed the newfangled microcontrollers and SoCs. And you also need to program the EEPROM, which is certainly doable without a processor, but well off the beaten path these days.