A FSM for reading floating point and integral numbers

Introduction

Here is a finite state machine(FSM) that can recognize integers and floating point numbers.

Example

0, 3962, 0.2053, 0.00053, 1.2962, 2965.9825

You may try to input some numbers below to see the result.

Trial Input


Result

3.1416

Source Code

<script> // handle user input function usrEnt(pInp) { var mInp = document.getElementById(pInp).value; var mRes = fsm(mInp); document.getElementById('frmOut03').innerHTML = mRes; } // finite state machine function fsm(pStr) { var mState = 'A'; var mch = ''; // key in char var mcc = 0; // ASCII code of key in char var mtoken = ''; var mRes = ''; for (var mi=0; mi<pStr.length; mi++) { mch = pStr.charAt(mi) mcc = mch.charCodeAt(0); // FSM if (mState=='A' && mcc==48) { // A: 0 -> C mtoken += mch; mState = 'C'; } else if (mState=='A' && mcc>=49 && mcc<=57) { // A: 1-9 -> B mtoken += mch; mState = 'B'; } else if (mState=='B' && mcc>=48 && mcc<=57) { // B: 0-9 -> B mtoken += mch; } else if (mState=='B' && mcc==46) { // B: . -> D mtoken += mch; mState = 'D'; } else if (mState=='C' && mcc==46) { // C: . -> D mtoken += mch; mState = 'D'; } else if (mState=='D' && mcc>=48 && mcc<=57) { // D: 0-9 -> D mtoken += mch; } else { mState = 'Err'; } } // handle the last token if (['B','C','D'].includes(mState)) { mRes = parseFloat(mtoken); } else { // invalid token mRes = 'Error'; } return mRes; } </script> <h3>Input Expression</h3> <input id='frmInp01' onKeyUp='usrEnt("frmInp01")' size='40'></br> <h3>Result</h3></br> <div id='frmOut03'></div>