'variation of BASIC example
w$="aebdef"
z$="cacbc"
print lcs$(w$,z$)

'output:
'ab

wait

FUNCTION lcs$(a$, b$)
    IF LEN(a$) = 0 OR LEN(b$) = 0 THEN
        lcs$ = ""
        exit function
    end if

    IF RIGHT$(a$, 1) = RIGHT$(b$, 1) THEN
        lcs$ = lcs$(LEFT$(a$, LEN(a$) - 1), LEFT$(b$, LEN(b$) - 1)) + RIGHT$(a$, 1)
        exit function
    ELSE
        x$ = lcs$(a$, LEFT$(b$, LEN(b$) - 1))
        y$ = lcs$(LEFT$(a$, LEN(a$) - 1), b$)
        IF LEN(x$) > LEN(y$) THEN
            lcs$ = x$
            exit function
        ELSE
            lcs$ = y$
            exit function
        END IF
    END IF
END FUNCTION