Contents

Argument syntax

  • number * count. Example: "5*3" ⟹ [5, 5, 5]
  • begin-end. Example: "1-3" ⟹ [1, 2, 3]
  • begin-end/step. Example: "1-5/2" ⟹ [1, 3, 5]

"1, 2-10/2, 5*3" ⟹ [ 1, 2, 4, 6, 8, 10, 5, 5, 5 ]

range()

Return range from begin to end (inclusive).

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> Array.from(range(0, 3))
[ 0, 1, 2, 3 ]
> Array.from(range(0, 6, 2))
[ 0, 2, 4, 6 ]
> Array.from(range(3, 0))
[ 3, 2, 1, 0 ]
> Array.from(range(6, 0, 2))
[ 6, 4, 2, 0 ]

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function* range(begin, end, step=1) {
    if (begin <= end) {
        while (begin <= end) {
            yield begin;
            begin += step;
        }
    } else {
        while (begin >= end) {
            yield begin;
            begin -= step;
        }
    }
}

syntax()

Hash table containing regular expressions and routines for parsing them.

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const syntax = {
    // `number * count`
    '^\-?[0-9]+\\*\-?[0-9]+$': function(s) {
        let [n, rep] = s.split('*').map(Number);
        return Array.apply(null, Array(rep)).map(elt => n);
    },
    // `begin-end`
    '^\-?[0-9]+\-{1}\-?[0-9]+$': function(s) {
        let a = Number(/^\-?[0-9]+/.exec(s)[0]);
        let b = Number(/\-(\-?[0-9]+)$/.exec(s)[1]);
        return Array.from(range(a, b));
    },
    // `begin-end/step`
    '^\-?[0-9]+\-{1}\-?[0-9]+\\/\-?[0-9]+$': function(s) {
        let a = Number(/^\-?[0-9]+/.exec(s)[0]);
        let b = Number(/\-(\-?[0-9]+)\//.exec(s)[1]);
        let step = Number(/\/(\-?[0-9]+)$/.exec(s)[1]);
        return Array.from(range(a, b, step));
    }
};

parse()

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const parse = function(s) {
    for (let exp of Object.keys(syntax)) {
        if (new RegExp(exp).test(s)) {
            return syntax[exp](s);
        }
    }
    return Number(s);
};

encode()

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const encode = s =>
    [].concat.apply([], s.split(',').map(elt => parse(elt.trim())));

Example usage

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> encode('1, 2-10/2, 5*3')
[ 1, 2, 4, 6, 8, 10, 5, 5, 5 ]