regular language - How does "δ:Q×Σ→Q" read in the definition of a DFA (deterministic finite automaton)? -
how δ: q × Σ → q in english? describing × , → mean help.
δ a mathematical function called transition function . like.
z = f(x, y) a function in mathematical defines mapping of elements in 1 set set. in function set of input arguments called domain of function , output rage.
[answer]
in expression "δ:q×Σ → q",
× means cartesian product (that set), , → mapping.
"δ:q×Σ → q"saysδtransition function defined mappingq×Σq. where, domain ofδq × Σ, rangeq.
note: cartesian product mathematical possible order pair (mapping) between 2 sets.
you can say:
δtransition function defined mapping between(or associates) cartesian product of set of statesq, language symbolsΣset of stateq. abbreviated δ: q×Σ → q
here, q finite set of states , Σ finite set of language symbols.
additionally in automated can represent transition function in tree ways.
1. transition table
2. transition graph or state diagram.
3. transition function: finite set of mapping rules. e.g. {δ(q0, a) → q1, δ(q1, a) → q2}
all same purpose define maping
in dfa. δ:q×Σ → q can written δ(q,Σ) → q it's similar function. in δ function 2 input arguments state q , language symbol Σ , returned value q.
what meaning of δ(q,Σ) → q
suppose in set of transition function δ have element δ(q0, a) → q1 means. if present state q0 consuming a symbol can shift state q1. , state-diagram δ(q0, a) → q1:
(q0)---a---►(q1) and transition table is:
+----+----+ |q\Σ | | +----+----+ | q0 | q1 | +----+----+ and defines mapping (q0, a) (q1).
some authors write
δ ⊆ q×Σ → qin formal dfa definition meansδpartial function (not defined on full domainq×Σ). can definedδon full domain required sometime example find complement dfa. here(complement dfa), wrote 2 dfas same language 1 partial dfa other complement dfa.
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