为了完成java的作业，先拿js写了一个。暂时只完成了一些简单的运算
效果：
1 2 3 4 5 6 7 | expression.calcExpression('1%+1');//1.01 expression.calcExpression('.1%+1');//1.001 expression.calcExpression('(5-2)%/0');//Infinity expression.calcExpression('(4+3)(4-3)');//7 expression.calcExpression('3(4+5)');//27 expression.calcExpression('-3(4+5)');//-27 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 | /* Copyright [email protected] (https://luojia.me) */ class expression{ static throwError(index){ throw(`expression error @${index}`); } static compItem(value,index){ return [value,index]; } static isNumber(item){ return typeof item[0]==='number'; } static calcExpression(exp){ let rawcomps=[], comps=[]; let signs=new RegExp(/[\(\)\-\+\*\/\%]/y), space=new RegExp(/\s+/y), number=new RegExp(/(\d+\.*\d*)|(\.\d+)/y); let lastIndex=0,match; do{ if(((space.lastIndex=lastIndex),true)&&(match=space.exec(exp))){//spaces rawcomps.push(match[0]); lastIndex=space.lastIndex; }else if(((signs.lastIndex=lastIndex),true)&&(match=signs.exec(exp))){//signs rawcomps.push(match[0]); comps.push(expression.compItem(match[0],match.index)); if(match[0]==='('){ if(comps.length>1){ let last=comps[comps.length-2][0]; if(last===')'|| expression.isNumber(comps[comps.length-2])){ comps.splice(comps.length-1,0,expression.compItem('*',-1)); } } } lastIndex=signs.lastIndex; }else if(((number.lastIndex=lastIndex),true)&&(match=number.exec(exp))){//number rawcomps.push(match[0]); if(match[0][0]==='.')match[0]='0'+match[0];//添加0 comps.push(expression.compItem(Number(match[0]),match.index)); lastIndex=number.lastIndex; }else{ expression.throwError(lastIndex); } }while(lastIndex!==exp.length); return expression.expressionParser(comps)[0]; } static expressionParser(comps){//return a compItem let groupStack=[],lastWasNumber=false; for(let i=0;i<comps.length;i++){//() if(expression.isNumber(comps[i])){ if(lastWasNumber)expression.throwError(comps[i][1]); lastWasNumber=true; continue; } lastWasNumber=false; if(comps[i][0]==='('){ groupStack.push(i); }else if(comps[i][0]===')'){ if(groupStack.length===0) expression.throwError(comps[i][1]); else if(groupStack.length===1){//use a new parser let newgroup=comps.splice(groupStack[0],i-groupStack[0]+1); newgroup.pop();newgroup.shift(); comps.splice(groupStack[0],0,expression.expressionParser(newgroup)); i=groupStack[0]; } groupStack.pop(); } } if(groupStack.length)expression.throwError(comps[groupStack[groupStack.length-1]][1]); for(let i=0;i<comps.length;i++){// n% if(expression.isNumber(comps[i])){continue;} let exp=comps[i][0]; if(exp==='%'){ if(!comps[i-1] || !expression.isNumber(comps[i-1]))expression.throwError(comps[i][1]); comps.splice(i-1,2,expression.compItem(comps[i-1][0]/100,comps[i-1][1])); i--; } } for(let i=0;i<comps.length;i++){// * / if(expression.isNumber(comps[i])){continue;} let exp=comps[i][0]; if(exp==='*'||exp==='/'){ if(i===comps.length || !comps[i-1] || !expression.isNumber(comps[i-1]) || !expression.isNumber(comps[i+1])) expression.throwError(comps[i][1]); //calc let result; if(exp==='*'){ result=comps[i-1][0]*comps[i+1][0]; }else{ result=comps[i-1][0]/comps[i+1][0]; } comps.splice(i-1,3,expression.compItem(result,comps[i-1][1])); i--; } } for(let i=0;i<comps.length;i++){// + - if(expression.isNumber(comps[i])){continue;} let exp=comps[i][0]; if(exp==='+'||exp==='-'){ if(i===comps.length || !expression.isNumber(comps[i+1])) expression.throwError(comps[i][1]); if(i===0||!expression.isNumber(comps[i-1])){//当做正负符号 if(exp==='-')comps[i+1][0]=-comps[i+1][0]; comps.splice(i,1); i--; }else{//计算表达式 let result; if(exp==='+'){ result=comps[i-1][0]+comps[i+1][0]; }else{ result=comps[i-1][0]-comps[i+1][0]; } comps.splice(i-1,3,expression.compItem(result,comps[i-1][1])); i--; } } } if(comps.length!==1){ console.error([...comps]); throw('something wrong'); } return comps[0];//return the value } } |
如文中无特殊说明，本站均使用以下协议：
知识共享署名-非商业性使用-禁止演绎 4.0 国际许可协议进行许可。
本博客使用Disqus评论系统，如果看不到评论框，请尝试爬墙。
