PROGRAM hopfield
DIM T(50,50)
CALL memorize(T(,),N)
DO
   CALL recall(T(,),N)
LOOP
END

SUB memorize(T(,),N)
    DIM V(50)
    RANDOMIZE
    INPUT prompt "number of stored memories = ": M
    ! N corresponds to number of neurons
    INPUT prompt "size of memories = ": N
    PRINT "enter M strings of N 0's and 1's"
    FOR memory = 1 to M
        LINE INPUT s$
        CALL convert(s$,N,V())
        FOR i = 1 to N
            FOR j = 1 to N
                IF i <> j then
                   LET T(i,j) = T(i,j) + (2*V(i) - 1)*(2*V(j) - 1)
                END IF
            NEXT j
        NEXT i
    NEXT memory
    PRINT
END SUB

SUB recall(T(,),N)
    DIM V(50)
    PRINT "enter a string of N 0's and 1's"
    LINE INPUT s$
    CALL convert(s$,N,V())
    DO
       FOR k = 1 to N
           LET i = int(N*rnd) + 1      ! choose neuron at random
           LET sum = 0
           FOR j = 1 to N
               IF i <> j then LET sum = sum + T(i,j)*V(j)
           NEXT j
           IF sum > 0 then
              LET V(i) = 1        ! above threshold 
           ELSE
              LET V(i) = 0        ! below threshold 
           END IF
       NEXT k
       FOR i = 1 to N
           PRINT using "#": V(i);
       NEXT i
       PRINT
       PAUSE 1
    LOOP until key input
    GET KEY kk
END SUB

SUB convert(s$,N,V())
    ! convert string to array of 0's and 1's
    FOR i = 1 to N
        LET c$ = s$[i:i]
        IF c$ = "0" then
           LET V(i) = 0
        ELSE
           LET V(i) = 1
        END IF
    NEXT i
END SUB