string.js
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	import number from "./number.js";

	var reA = /[-+]?(?:\d+\.?\d*\|\.?\d+)(?:[eE][-+]?\d+)?/g,
	reB = new RegExp(reA.source, "g");

	function zero(b) {
	return function() {
	return b;
	};
	}

	function one(b) {
	return function(t) {
	return b(t) + "";
	};
	}

	export default function(a, b) {
	var bi = reA.lastIndex = reB.lastIndex = 0, // scan index for next number in b
	am, // current match in a
	bm, // current match in b
	bs, // string preceding current number in b, if any
	i = -1, // index in s
	s = [], // string constants and placeholders
	q = []; // number interpolators

	// Coerce inputs to strings.
	a = a + "", b = b + "";

	// Interpolate pairs of numbers in a & b.
	while ((am = reA.exec(a))
	&& (bm = reB.exec(b))) {
	if ((bs = bm.index) > bi) { // a string precedes the next number in b
	bs = b.slice(bi, bs);
	if (s[i]) s[i] += bs; // coalesce with previous string
	else s[++i] = bs;
	}
	if ((am = am[0]) === (bm = bm[0])) { // numbers in a & b match
	if (s[i]) s[i] += bm; // coalesce with previous string
	else s[++i] = bm;
	} else { // interpolate non-matching numbers
	s[++i] = null;
	q.push({i: i, x: number(am, bm)});
	}
	bi = reB.lastIndex;
	}

	// Add remains of b.
	if (bi < b.length) {
	bs = b.slice(bi);
	if (s[i]) s[i] += bs; // coalesce with previous string
	else s[++i] = bs;
	}

	// Special optimization for only a single match.
	// Otherwise, interpolate each of the numbers and rejoin the string.
	return s.length < 2 ? (q[0]
	? one(q[0].x)
	: zero(b))
	: (b = q.length, function(t) {
	for (var i = 0, o; i < b; ++i) s[(o = q[i]).i] = o.x(t);
	return s.join("");
	});
	}

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