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Add range operator and documentation (#3346)
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core/modules/filters/range.js
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core/modules/filters/range.js
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/*\
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title: $:/core/modules/filters/range.js
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type: application/javascript
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module-type: filteroperator
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Filter operator for generating a numeric range.
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\*/
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(function(){
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/*jslint node: true, browser: true */
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/*global $tw: false */
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"use strict";
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/*
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Export our filter function
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*/
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exports.range = function(source,operator,options) {
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var results = [];
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// Split the operand into numbers delimited by these symbols
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var parts = operator.operand.split(/[,:;]/g), beg, end, inc, i, fixed = 0;
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for (i = 0; i < parts.length; ++i) {
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// Validate real number
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if (!/^\s*[+-]?((\d+(\.\d*)?)|(\.\d+))\s*$/.test(parts[i]))
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return ["range: bad number \""+parts[i]+"\""];
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// Count digits; the most precise number determines decimal places in output.
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var frac = /\.\d+/.exec(parts[i]);
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if (frac) fixed = Math.max(fixed, frac[0].length-1);
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parts[i] = parseFloat(parts[i]);
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}
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switch (parts.length) {
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case 1:
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beg = 0;
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end = parts[0];
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inc = 1;
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break;
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case 2:
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beg = parts[0];
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end = parts[1];
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inc = 1;
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break;
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case 3:
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beg = parts[0];
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end = parts[1];
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inc = Math.abs(parts[2]);
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break;
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}
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if (inc === 0) return ["range: increment 0 causes infinite loop"];
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// May need to count backwards
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var direction = ((end<beg) ? -1 : 1);
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inc *= direction;
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// Estimate number of resulting elements
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if ((end-beg)/inc > 10000) return ["range: too many steps (over 10K)"];
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// Avoid rounding error on last step
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end += direction * 0.5 * Math.pow(0.1, fixed);
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var safety = 10010;
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// Enumerate the range
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if (end<beg) {for (i = beg; i > end; i += inc) {results.push(i.toFixed(fixed)); if (--safety<0) break;}}
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else {for (i = beg; i < end; i += inc) {results.push(i.toFixed(fixed)); if (--safety<0) break;}}
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if (safety<0) return ["range: unexpectedly large output"];
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// Reverse?
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if (operator.prefix === "!") results.reverse();
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return results;
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};
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})();
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59
editions/tw5.com/tiddlers/filters/range.tid
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59
editions/tw5.com/tiddlers/filters/range.tid
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created: 20171221184734665
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modified: 20171229211834620
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tags: [[Filter Operators]] [[Negatable Operators]]
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title: range Operator
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type: text/vnd.tiddlywiki
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caption: range
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op-purpose: generate a range of numbers
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op-input: ignored
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op-parameter: a range specification, like `[1,5]`
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op-parameter-name: N
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op-output: a series of evenly spaced numbers ranging from `<begin>` to `<end>`
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\define range_example(range)
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```
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[range[$range$]]
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```
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<$list variable=n filter="[range[$range$]]"><<n>> </$list>
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\end
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The `range` operator allows a range of numbers to be enumerated, similar to a `for` loop in other programming languages. It's useful in combination with the [[Formula Plugin]].
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|!Purpose|produce a range of numbers|
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|!Input|ignored.|
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|!Parameter|1-3 numbers separated by `,` or `;`.|
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|!Output|A range of numbers starting with |
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|!`!` Output|As ''Output'', but with order reversed.|
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The parameter has three forms:
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* `<end>`
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* `<begin>,<end>`
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* `<begin>,<end>,<step>`
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Each part must be a number, and works as follows:
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* `<begin>`: start counting at this number. Defaults to 0.
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* `<end>`: stop counting at this number.
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** It will be included unless it falls between two steps.
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* `<step>`: count up (or down) by this amount.
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** It may be negated so it counts in the right direction.
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** It cannot be zero.
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The number of decimal points in the output is fixed, and based on the parameter with the //most// decimal points.
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To prevent the browser from freezing, `range` is currently limited to 10,000 values.
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!!Examples
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<<range_example "7">>
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<<range_example "1, 10">>
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<<range_example "17,13">>
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<<range_example "1.001, 5, 1">>
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<<range_example ".5,1.4,.004">>
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