Tiny Calculator 01

This is a tiny calculator.

• Only accept integers input
• Operations: + - * /
• Perform * and / before + and -
• c : reset
• Ent : evaluate

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Successful Examples:

• 3 + 4 * 5 Ent -> 23
• 3 + 4 + 5 Ent -> 12
• 32 + 45 - 18 Ent -> 59
• 3 * 4 * 5 Ent -> 60
• 3 + 4 * 5 * 2 Ent -> 43
• 3 + 4 * 5 * 2 - 21 Ent -> 22
• 72 - 4 * 12 + 6 / 3 * 19 Ent -> 62
• 3 + 4 * 12 Ent - 99 Ent -> -48

Failed Examples:

• 3 + -

Source Code

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// calculator01b class var cal01b=function() { // registers this.op1=''; // operand 1 this.op2=''; // operand 2 this.opr=''; // operator this.mop1=''; // memorized operand 1 this.mopr=''; // memorized operator this.scr=''; // screen output this.flg1=false; // flag 1 this.reset(); } // reset all registers cal01b.prototype.reset = function(){ this.op1=''; this.op2=''; this.opr=''; this.mop1=''; this.mopr=''; this.scr='0'; this.flg1=false; } // reset memorized registers // for low priority operation cal01b.prototype.resetm = function(){ this.mop1=''; this.mopr=''; } // binary operations // pop1 : string = operand 1 // popr : string = operator // pop2 : string = operand 2 // return : string = result of operation cal01b.prototype.binOperation = function(pop1,popr,pop2) { var mn; var mop1=parseFloat(pop1); var mop2=parseFloat(pop2); switch(popr) { case '': mn=mop2; break; case '+': mn=mop1+mop2; break; case '-': mn=mop1-mop2; break; case '*': mn=mop1*mop2; break; case '/': mn=mop1/mop2; break; } return mn.toString(); } // state machine handling keycode // pCode : int = keycode cal01b.prototype.stateMachine = function(pCode) { var mCodeStr = String.fromCharCode(pCode); if (pCode==99) { // c this.reset(); } else if (pCode>=48 && pCode<=57) { // 0-9 if (this.flg1) { this.op2=''; this.flg1=false; } // build up operand 2 this.op2+=mCodeStr; this.scr=this.op2; } else if (pCode==43 || pCode==45) { // +|- // high priority operation this.op1=this.binOperation( this.op1,this.opr,this.op2); // low priority operation this.op1=this.binOperation( this.mop1,this.mopr,this.op1); this.resetm(); // this.opr=mCodeStr; this.op2=''; this.scr=this.op1; } else if (pCode==42 || pCode==47) { // *|/ if (this.opr=='+'||this.opr=='-') { // save low priority operation this.mopr=this.opr; this.mop1=this.op1; this.opr=mCodeStr; this.op1=this.op2; this.op2=''; } else { // high priority operation this.op1=this.binOperation( this.op1,this.opr,this.op2); this.opr=mCodeStr; this.op2=''; this.scr=this.op1; } } else if (pCode==13) { // Enter if (this.op2=='') { return; } // high priority operation this.op1=this.binOperation( this.op1,this.opr,this.op2); this.op1=this.binOperation( this.mop1,this.mopr,this.op1); this.scr=this.op1; this.opr=''; this.resetm(); this.op2=this.op1; this.op1=''; this.flg1=true; } } // end of calculator01b class var cnvwidth = 0; var cnvheight = 0; var context, canvas; var keycode; // debug function init() { canvas = document.getElementById("myCanvas"); context = canvas.getContext("2d"); cnvwidth = canvas.width; cnvheight = canvas.height; mcal = new cal01b(); keycode=0; // debug window.addEventListener('keypress', doKeyPress); return setInterval(draw, 100); } function doKeyPress(pE) { var mkey = pE.keyCode || pE.which; keycode = mkey; // debug mcal.stateMachine(mkey); } function draw() { context.clearRect(0,0,cnvwidth,cnvheight); // draw score context.save(); context.font = "bold 10pt Sans-Serif"; context.fillText("Key Code: "+keycode, 300, 20); context.fillText("op2: "+mcal.op2, 250, 50); context.fillText("op1: "+mcal.op1, 50, 50); context.fillText("opr: "+mcal.opr, 150, 50); context.fillText("mop1: "+mcal.mop1, 50, 80); context.fillText("mopr: "+mcal.mopr, 150, 80); context.font = "bold 14pt Sans-Serif"; context.textAlign='end'; context.fillText(mcal.scr, 380, 140); context.lineWidth = 1; context.strokeRect(40,100,350,50); // context.font = "bold 10pt Sans-Serif"; var mp=mcal.opr; if (mp=='-') {mp='\u2212';} else if (mp=='*') {mp='\u00d7';} else if (mp=='/') {mp='\u00f7';} context.fillText(mp, 380, 115); context.restore(); } init();