project Abeona #2

作者: 放假广告 | 来源:发表于2018-10-14 09:16 被阅读0次

Scanner:

character-by-character formulation:
recognizing "new" pseudocode:

c <- NextChar();
if ( c = 'n')
    then begin:
        c <- NextChar();
        if ( c = 'e' )
            then begin:
                c <- NextChar();
                if ( c = 'w' )
                    then report success;
                    else try something else;
                end;
                else try something else;
            end;
            else try something else;

-> S0 -'n'-> S1 -'e'-> S2 -'w'-> S3 (to recognize "new")
-> S0 -'n'-> S1 -'e'-> S2 -'w'-> S3
\-'o'-> S4 -'t'-> S5 (to recognize "new" and "not")

Finite Automata:
Formal mathematical objects for above recognizer.
(S, $\Sigma$ , $\delta$ , s₀, S_A)
S is the finite set of states in the recognizer, along with an error state s_e.
$\Sigma$ is the finite alphabet used by the recognizer, the union of the edge labels in the transition diagram.
$\delta(s, c)$ is the recognizer's transition function. It maps each state $s\in S$ and each character $c \in \Sigma$ into some next state.
$s_0\in S$ is the designate start state.
$S_A$ is the set of accepting states, $S_A\subseteq S$ .