tcl-js/src/math/expression-to-string.js

tcl-js is a tcl intepreter written completely in Typescript. It is meant to replicate the tcl-sh interpreter as closely as possible.

import { INUMBER, IOP1, IOP2, IOP3, IVAR, IFUNCALL, IEXPR, IMEMBER } from './instruction';

export default function expressionToString(tokens, toJS) {
  var nstack = [];
  var n1, n2, n3;
  var f;
  for (var i = 0; i < tokens.length; i++) {
    var item = tokens[i];
    var type = item.type;
    if (type === INUMBER) {
      if (typeof item.value === 'number' && item.value < 0) {
        nstack.push('(' + item.value + ')');
      } else {
        nstack.push(escapeValue(item.value));
      }
    } else if (type === IOP2) {
      n2 = nstack.pop();
      n1 = nstack.pop();
      f = item.value;
      if (toJS) {
        if (f === '^') {
          nstack.push('Math.pow(' + n1 + ', ' + n2 + ')');
        } else if (f === 'and') {
          nstack.push('(!!' + n1 + ' && !!' + n2 + ')');
        } else if (f === 'or') {
          nstack.push('(!!' + n1 + ' || !!' + n2 + ')');
        } else if (f === '||') {
          nstack.push('(String(' + n1 + ') + String(' + n2 + '))');
        } else if (f === '==') {
          nstack.push('(' + n1 + ' === ' + n2 + ')');
        } else if (f === '!=') {
          nstack.push('(' + n1 + ' !== ' + n2 + ')');
        } else {
          nstack.push('(' + n1 + ' ' + f + ' ' + n2 + ')');
        }
      } else {
        nstack.push('(' + n1 + ' ' + f + ' ' + n2 + ')');
      }
    } else if (type === IOP3) {
      n3 = nstack.pop();
      n2 = nstack.pop();
      n1 = nstack.pop();
      f = item.value;
      if (f === '?') {
        nstack.push('(' + n1 + ' ? ' + n2 + ' : ' + n3 + ')');
      } else {
        throw new Error('invalid Expression');
      }
    } else if (type === IVAR) {
      nstack.push(item.value);
    } else if (type === IOP1) {
      n1 = nstack.pop();
      f = item.value;
      if (f === '-' || f === '+') {
        nstack.push('(' + f + n1 + ')');
      } else if (toJS) {
        if (f === 'not') {
          nstack.push('(' + '!' + n1 + ')');
        } else if (f === '!') {
          nstack.push('fac(' + n1 + ')');
        } else {
          nstack.push(f + '(' + n1 + ')');
        }
      } else if (f === '!') {
        nstack.push('(' + n1 + '!)');
      } else {
        nstack.push('(' + f + ' ' + n1 + ')');
      }
    } else if (type === IFUNCALL) {
      var argCount = item.value;
      var args = [];
      while (argCount-- > 0) {
        args.unshift(nstack.pop());
      }
      f = nstack.pop();
      nstack.push(f + '(' + args.join(', ') + ')');
    } else if (type === IMEMBER) {
      n1 = nstack.pop();
      nstack.push(n1 + '.' + item.value);
    } else if (type === IEXPR) {
      nstack.push('(' + expressionToString(item.value, toJS) + ')');
    } else {
      throw new Error('invalid Expression');
    }
  }
  if (nstack.length > 1) {
    throw new Error('invalid Expression (parity)');
  }
  return String(nstack[0]);
}

function escapeValue(v) {
  if (typeof v === 'string') {
    return JSON.stringify(v).replace(/\u2028/g, '\\u2028').replace(/\u2029/g, '\\u2029');
  }
  return v;
}