arraynge

Various transforms for ranges of array/list indices.

Usage

see test/usage.js

API

Import it

var arraynge = require('arraynge');

Create arraynges

range = arraynge();
range = arraynge(from, upto);           // range includes both values
range = arraynge(from, upto, list);
 
makeRangeFromList = arraynge.withThisList.bind(list);
range = makeRangeFromList(from, upto);
 
list.makeRange = arraynge.withThisList;
range = list.makeRange(from, upto);

Configure an arraynge

The config functions return the arraynge they were called on, so you can chain them.

range.bounds(newFirstIndex, newLastIndex);
range.from(newFirstIndex);
range.upto(newLastIndex);
range.list(null || false);  // forget current list
range.list(someObject);     // set new list
range.list(someNumber);     // set list to object { length: someNumber }

Query the config

range.toString();   // -> (string) description
range.bounds();     // -> (array) [from, upto]
range.from();       // -> (any) from
range.upto();       // -> (any) upto
range.list();       // -> (object | false) list
range.len();        // -> (number) list.length or 0

Modify the bounds

Parameter max or len is optional. If provided, it should be a number. (Maximum valid integer index for your list, or the list's length.) If not provided or undefined, it is calculated from .len().

range.trueMax(max);   // index === true? set to max.
range.warpZero(len);  // index negative? += len. still neg? set to false.
range.modulo(len);    // warp indices into range [0 <= x < len]
range.confine(max);   // index negative? set to 0. too large? set to max.
 
range.validateBounds(max);    // negative or too large? set to false.
 
range.translate(bothDist);            // add same offset to both
range.translate(fromDist, lastDist);  // add offsets to each

Cautious transforms

• They won't modify the config.
• If any of the bounds is not a finite number, or is out of range, the cautious transforms will abort without any action or side effect and will return false.
• Parameters len or max optional as above.

range.boundsIfValid(max);   // array [from, upto]
range.enumerate();    // array of numbers {from <= x <= upto}, step size = 1
range.map(iter);      // numbers like .enumerate but collect iter(list[x], x)

License

ISC