A bit of fun for SpahQL.js - Matching ruby's range operations for strings in Javascript.

ruby_string_range_in_javascript.js

evalStringRange: function(start, end) {
      var results = [];
      
      // Figure out if this is a reversed or symmetrical range. 
      // Another easy comparison: Symmetrical ranges have one entry
      if(start == end) return [start];
      // Easy comparison: One string is shorter than the other or the range is reversed
      if((start > end)||(start.length!=end.length)) return results; 
      
      // Columnar charcode indexes:
      // integer: 48..57 == "0".."9"
      // ucase: 65..90 == "A".."Z"
      // lcase: 97..122 == "a".."z"
      
      // We're going to treat this like a slot machine. 
      // Create an array of "locks" which are locked columns in the range.
      var locks = [];
      var allLocked = true;
      for(var c=0; c<start.length; c++) {
        var code = start.charCodeAt(c);
        // If outside of range, lock
        locks[c] = ((code >= 48 && code <= 57) || (code >= 65 && code <= 90) || (code >= 97 && code <= 122))? false : true;
        allLocked = (locks[c]==true && allLocked==true);
        // If all others are locked and this is last column, unlock
        if(allLocked && c == start.length-1) locks[c] = false;
      }
            
      var nextWorkingCol = function(wC) {
        for(var w=wC-1; w>-2; w--) {
          if(locks[w] == false) return w;
        }
      }
      
      var gen = start+""; // clone start
      iterating: while(true) {
        // ^^^^
        // When the workingCol hits -1 we know we popped a carry on the highest-order digit and maxed the string
        // If nextString == end then we hit the range target and should break.
        // Push the last-iterated result
        //results.push(new Spah.SpahQL.QueryResult(null, gen));
        results.push(gen);
        if(gen == end) break iterating;
        
        // Iterate until carrying stops, giving us our new stop value for the next increment
        var workingCol = nextWorkingCol(start.length),
            carry = true,
            next = "";        
        
        carrying: while(true) {
          // Iterate start string and push new results. Break on maxing all unlocked columns or on reaching end token.
          // Iteration works on the lowest-order unlocked column and may generate a carry operation, which resets the current working
          // column to its lowest value and increments the next highest-order unlocked column. This in turn may generate a carry operation.
          // If the overall highest-order unlocked column generates a carry when incremented, then the string is maxed and the range
          // terminates.
          next = (function(str) {
              // Iterates a character and generates a new string and potentially a carry.
              var carry = false;
              var cCode = str.charCodeAt(0);
              var nCode;
              if(cCode == 57) {
                carry = true;
                nCode = 48;
              }
              else if(cCode == 90) {
                carry = true;
                nCode = 65;
              }
              else if(cCode == 122) {
                carry = true;
                nCode = 97;
              }
              else if(cCode == 127) {
                carry = true;
                nCode = cCode;
              } 
              else {
                nCode = cCode+1;
              }
              return [String.fromCharCode(nCode), carry];
          })(gen.charAt(workingCol));
          
          gen = gen.split(""); gen.splice(workingCol,1,next[0]); gen = gen.join("");
          if(next[1]==true) {
            // Next next highest-order unlocked col
            workingCol = nextWorkingCol(workingCol);
            if(workingCol < 0) break iterating;
          }
          else {
            break carrying;
          }
        }
      }
      
      return results;
    }