var vars = []; var currentLine = 0; function isValidName(name){ var m = name.match("^[_a-zA-Z][_a-zA-Z0-9]*$"); if (m===null){ //printError("invalid variable name "+name); return false; } return true; } function isValidNumber(str){ var m = str.match("^[\\-]?\\d+(\\.\\d*)?$"); // var m = str.match("\\d+"); if (m===null){ //printError("<"+str + ">: invalid number"); return false; } //println("number: " + parseFloat(str)); return true; } function isValidString(str){ var m = str.match("^\\\"(.*)\\\"$"); // var m = str.match("\\d+"); if (m===null){ //printError("<"+str + ">: invalid number"); return false; } // println("string: " + m[1]); return m[1]; } function findName(name){ for (var i = 0; i " + vars[idx].value); return vars[idx].value; } function calc(expr){ if (expr===null || expr===undefined) return null; var ret = null; var m = expr.match("(\\S+)\\s*([\\+\\-\\*\\/])\\s*(\\S+)\\s*"); if (m!==null){ //println("calc("+m[1]+","+m[2]+","+m[3]+")"); var op1 = calc(m[1]); if (op1 === null) { printError("illegal operand 1 ("+m[1]+")"); return null; } var op2 = calc(m[3]); if (op2 === null) { printError("illegal operand 2 ("+m[3]+")"); return null; } if (m[2]=='*') ret = op1 * op2; else if (m[2]=='/') ret = op1 / op2; else if (m[2]=='+') ret = op1*1 + op2; else if (m[2]=='-') ret = op1 - op2; return ret; } //println("calc("+expr+")"); if (isValidNumber(expr)){ ret = parseFloat(expr); //println("calc returns number: "+ret); } else if (isValidName(expr)) { ret = getValue(expr); //println("calc returns value: "+ret); } var s = isValidString(expr); if (s!==false) ret = s; // println("calc returns value: "+ret); if (ret === null) printError("syntax error ("+expr+")"); return ret; } function print(t){ document.getElementById("output").innerHTML+=t; } function println(t){ print (t+"
\n"); } function printError(t){ println ("Error at line "+currentLine+": "+t+"\n"); } function clearOutput(){ document.getElementById("output").innerHTML=""; } function parse(line){ var m; m = line.match("svar\\s+(\\S+)[\\s]*;"); if (m!==null){ addVar(m[1]); return 0; } m = line.match("print\\s+(\\S.+\\S)\\s*;"); if (m!==null){ //console.log("print ("+m[1]+"): " + calc(m[1])); var p = calc(m[1]); if(p!==null) println(calc(m[1])); return 0; } m = line.match("(\\S+)\\s*=\\s*(.*\\S)*\\s*;"); if (m!==null){ //println("<"+m[2]+">"); setValue(m[1], calc(m[2])); return 0; } printError("syntax error ("+line+")"); } function readProg(){ clearOutput(); currentLine = 0; var lines = document.getElementById("src").value.split("\n"); lines.forEach(function (e){ currentLine++; parse(e); }); }

Simple Interpreter