unicodeExponent function
Returns the unicode symbols that represent an exponent.
Implementation
String unicodeExponent(num exp) {
final neg = exp < 0 ? '\u{207b}' : '';
final absExp = exp.abs();
final expStr = absExp.toString();
final buf = StringBuffer()..write(neg);
for (var place = 0; place < expStr.length; place++) {
buf.write(expUnicodeMap[expStr[place]]);
}
return buf.toString();
}