| |
| export function arithmeticExpression(input) { |
| if(typeof input!=='string'||input.length>1000)throw Error('EXPRESSION_BUDGET'); |
| const tokens=input.match(/Infinity|NaN|(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?|\*\*|[()+*/%-]|\S/g)||[]; |
| if(tokens.length>256)throw Error('TOKEN_BUDGET'); |
| let at=0,depth=0; |
| const take=()=>tokens[at++]; |
| function atom(){ |
| if(++depth>32)throw Error('DEPTH_BUDGET'); |
| let value; |
| if(tokens[at]==='('){take();value=sum();if(take()!==')')throw Error('MISSING_PAREN');} |
| else { |
| const token=take(); |
| if(!token||! /^(?:Infinity|NaN|(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?)$/.test(token))throw Error('EXPECTED_NUMBER'); |
| value=Number(token); |
| } |
| depth--;return value; |
| } |
| function power(){let v=atom();if(tokens[at]==='**'){take();v=v**unary();}return v;} |
| function unary(){ |
| if(tokens[at]==='+'||tokens[at]==='-'){ |
| const sign=take(); |
| if(tokens[at]===sign)throw Error('INCREMENT_NOT_ARITHMETIC'); |
| |
| if(tokens[at]!=='(' && tokens[at+1]==='**')throw Error('UNARY_EXPONENT_BASE'); |
| if(++depth>32)throw Error('DEPTH_BUDGET'); |
| const value=unary();depth--; |
| return sign==='-'?-value:value; |
| } |
| return power(); |
| } |
| function product(){let v=unary();while(['*','/','%'].includes(tokens[at])){const op=take(),r=unary();v=op==='*'?v*r:op==='/'?v/r:v%r;}return v;} |
| function sum(){let v=product();while(['+','-'].includes(tokens[at])){const op=take();if(tokens[at]===op)throw Error('INCREMENT_NOT_ARITHMETIC');const r=product();v=op==='+'?v+r:v-r;}return v;} |
| const value=sum();if(at!==tokens.length)throw Error('UNSUPPORTED_EXPRESSION');return value; |
| } |
|
|
