Welcome to SWI-Prolog (threaded, 64 bits, version 8.0.3) SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software. Please run ?- license. for legal details. For online help and background, visit http://www.swi-prolog.org For built-in help, use ?- help(Topic). or ?- apropos(Word). ?- consult(crypto_r). true. ?- recognizer. |: Use five and four and three and two and one to make zero. ok |: Use five and five and five and five and five to make five. ok |: Use one two three four and five to make six. ok |: Use one two three four five to make six. Not a sentence ... |: Write one in terms of the odd numbers. ok |: Write one in terms of the even numbers. Not a sentence ... |: Write zero in terms of two through six. Not a sentence ... |: Write zero in terms of numbers two through six. ok |: Can you make seven from the first five positive numbers? ok |: Use whatever to make whatever. ok |: Can you make three from two zeros and three ones? ok |: Can you make nine from one nine and four threes? ok |: Can you make nine from four threes and one nine? ok |: Can you make five from nine threes? Not a sentence ... |: Can you make 5 from 9 threes? Not a sentence ... |: ^C Action (h for help) ? abort % Execution Aborted ?- halt.