30:T459,rpn = (seq, arr) => { const ops = '+ - * / % & | ^ << >> > >= < <= == != && ||' .split(/\s+/) .reduce((res, e) => { res[e] = e; return res; }, {}); if (typeof seq === 'string') { seq = seq.split(/\s+/); } if (typeof arr === 'string') { arr = arr.split(/\s+/); } for (let j = 0; j < 100; j++) { for (let i = 0; i < seq.length; i++) { const cmd = seq[i]; if (ops[cmd]) { const rhs = arr.pop(); const lhs = arr.pop(); arr.push(`(${lhs} ${cmd} ${rhs})`); } else if (cmd.slice(0, -1) === '(' && ops[cmd.slice(1)]) { const lhs = arr.shift(); const rhs = arr.shift(); arr.unshift(`(${lhs} ${cmd.slice(1)} ${rhs})`); } else if (cmd === 'swap') { const rhs = arr.pop(); const lhs = arr.pop(); arr.push(rhs); arr.push(lhs); } else { const num = Number(cmd); if (!isNaN(num)) { arr.push(num); } } if (arr.length < 2) { return arr[0]; } } } return arr[0]; }31:[] 2e:{"title":"RPN","cells":[{"id":0,"value":"md`\n# RPN\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":180,"value":"md`\nBinary operations:\n\n * arithmetic ( \\`+ - * / %\\` )\n * bit-wise ( \\`& | ^\\` )\n * shift ( \\`<< >>\\` )\n * relational, equality, logical ( \\`> >= < <= == != && ||\\` )\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":183,"value":"rpn('+ *', 'a b')","pinned":true,"hidden":false,"mode":"ojs"},{"id":189,"value":"md`\nConstant literal can be pushed to the stack this way\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":191,"value":"rpn('42 -', 'a')","pinned":true,"hidden":false,"mode":"ojs"},{"id":194,"value":"md`\nThe order of operands is important for non-comutative operations. So \\`swap\\` word can be used to control emmidiate order.\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":73,"value":"rpn('swap -', 'a b')","pinned":true,"hidden":false,"mode":"ojs"},{"id":229,"value":"md`\nUnary operations:\n * negations ( \\`! ~\\` )\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":175,"value":"md`\n\n## Fold\n\nFolding array of elements into expression with given combining RPN sequence.\n\nFold : https://en.wikipedia.org/wiki/Fold_(higher-order_function)\n\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":152,"value":"md`\nNormal binary operations will perform right fold.\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":6,"value":"foldRightPlus = rpn('+', 'a b c d e f g h')","pinned":true,"hidden":false,"mode":"ojs"},{"id":154,"value":"md`\nBinary operations prefixed with left parenthesis '\\`(\\`' symbol will perform left fold.\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":97,"value":"foldLeftPlus = rpn('(+', 'a b c d e f g h')","pinned":true,"hidden":false,"mode":"ojs"},{"id":170,"value":"rpn('+', 'a b')","pinned":false,"hidden":false,"mode":"ojs"},{"id":4,"value":"$30","pinned":true,"hidden":false,"mode":"ojs"}],"files":"$W31","stdlib":"1","titling":"auto"}