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Simulators.js
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Simulators.js
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// @flow
import chalk from "chalk";
import { FSA } from "../interfaces/FSA.js";
import { State } from "../components/State.js";
import { DFA, NFA } from "../automata";
import { FSAUtils } from "../utils";
import { ErrorCode } from "../globals/errors.js";
import { instanceOf } from "../globals/globals.js";
export const simulateFSA = (
w: string | string[],
fsa: FSA,
logging: boolean = false,
returnEndState: boolean = false
): boolean | string | Array<string> => {
if (instanceOf(NFA, fsa)) {
return simulateNFA(w, fsa, new FSAUtils(NFA), logging, returnEndState);
} else {
return simulateDFA(w, fsa, new FSAUtils(DFA), logging, returnEndState);
}
};
export const stepOnceFSA = (
w: string,
qin: string | Array<string>,
fsa: FSA,
logging: boolean = false
): string | Array<string> => {
if (typeof w !== "string") {
if (logging) console.error(chalk.redBright("Input w was invalid type: %O"), w);
throw new TypeError();
}
if (typeof qin !== "string" && !Array.isArray(qin)) {
if (logging) console.error(chalk.redBright("Input state was invalid type: %O"), qin);
throw new TypeError();
}
// Step once
if (logging) console.log(chalk.inverse("Input Processing Started"));
let prevState: State | Array<State> = [];
if (typeof qin === "string") {
for (const state of fsa.getStates().values()) {
if (qin === state.name) prevState = state;
}
if (!prevState || (Array.isArray(prevState) && prevState.length === 0))
throw new Error(ErrorCode.INVALID_STATE_NAME);
} else {
prevState = [];
for (const state of fsa.getStates().values()) {
if (qin.includes(state.name)) prevState.push(state);
}
if (prevState.length !== qin.length) {
throw new Error(ErrorCode.INVALID_STATE_NAME);
}
}
let newState: State | Array<State>;
if (instanceOf(NFA, fsa)) newState = [...new FSAUtils(NFA).receiveInput(fsa, w, prevState)];
else newState = new FSAUtils(DFA).receiveInput(fsa, w, prevState);
if (logging) console.log("%o x '%s' -> %o", JSON.stringify(prevState), w, JSON.stringify(newState));
if (logging) console.log(chalk.inverse("Input Processing Ended"));
if (newState instanceof State) return newState.name;
else {
let retArray: Array<string> = [];
for (const _s of newState) {
retArray.push(_s.name);
}
return retArray;
}
};
/*
* Private methods
*/
function simulateDFA(
w: string | string[],
dfa: DFA,
utils: FSAUtils,
logging: boolean,
returnEndState: boolean
): boolean | string {
if (logging) console.log(chalk.cyan("Beginning DFA Simulation"));
//Accept either string or string[] for w
if (!Array.isArray(w)) {
if (typeof w === "string") w = [...w];
else {
if (logging) console.error(chalk.redBright("Input w was invalid type: %O"), w);
throw new TypeError();
}
}
// Step through the DFA
if (logging) console.log(chalk.inverse("Input Processing Started"));
let currentState: State = dfa.getStartState();
for (const char of w) {
const prevState: State = currentState;
currentState = utils.receiveInput(dfa, char, prevState);
if (logging) console.log("%o x '%s' -> %o", JSON.stringify(prevState), char, JSON.stringify(currentState));
}
if (logging) console.log(chalk.inverse("Input Processing Ended"));
// Check for acceptance
if (dfa.getAcceptStates().has(currentState)) {
if (logging) console.log(chalk.green("Input Accepted!"));
if (returnEndState) return currentState.name;
else return true;
} else {
if (logging) console.log(chalk.red("Input Rejected!"));
if (returnEndState) return currentState.name;
else return false;
}
}
function simulateNFA(
w: string | string[],
nfa: NFA,
utils: FSAUtils,
logging: boolean,
returnEndState: boolean
): boolean | Array<string> {
if (logging) console.log(chalk.cyan("Beginning NFA Simulation"));
//Accept either string or string[] for w
if (!(w instanceof Array)) {
if (typeof w === "string") {
if (w === "") w = [""];
else w = [...w];
} else {
if (logging) console.error(chalk.redBright("Input w was invalid type: %O"), w);
throw new TypeError();
}
}
if (logging) console.log(chalk.inverse("Input Processing Started"));
let currentState: Array<State> = [nfa.getStartState()];
for (const char of w) {
let prevState: Array<State> = currentState;
currentState = [...utils.receiveInput(nfa, char, currentState)];
if (logging) console.log("%o x '%s' -> %o", JSON.stringify(prevState), char, JSON.stringify(currentState));
}
if (logging) console.log(chalk.inverse("Input Processing Ended"));
/*
* Check for acceptance or rejection.
* If returnEndState:
* If accept, return all final accept states.
* If reject, return all final states or if no final state return empty string
*/
let retObj: Array<string> = [];
for (const _accState of nfa.getAcceptStates()) {
if (currentState.includes(_accState)) {
if (!returnEndState) {
if (logging) console.log(chalk.green("Input Accepted!"));
return true;
}
retObj.push(_accState.name);
}
}
if (retObj.length > 0) {
if (logging) console.log(chalk.green("Input Accepted!"));
return retObj;
}
if (logging) console.log(chalk.red("Input Rejected!"));
if (returnEndState) {
if (currentState.length > 0) {
for (const _cState of currentState) retObj.push(_cState.name);
}
return retObj;
} else {
return false;
}
}