Number sets in HTML and Unicode

When I started blogging I was very cautious about what characters I used because browsers often didn't have font support for uncommon characters. Things have changed since then and I've gotten less cautious. Nobody has complained, so I assume readers are seeing the characters I intend them to see.

There are Unicode characters for sets of numbers such as the integers and the real numbers, double-struck letters similar to the blackboard bold letters \mathbb{Z} etc. in LaTeX.

Here's a table of the characters, their Unicode values, and two HTML entities associated with each.

  U+2115 ℕ ℕ  U+2124 ℤ ℤ  U+211A ℚ ℚ  U+211D ℝ ℝ  U+2102 ℂ ℂ  U+210D ℍ ℍ

If you're going to use these symbols, you will likely also need to use (U+2208, ∈) and (U+2209, ∉).

More letters

If you want more letters in the style of those above, you can find them starting at U+1D538 for . However, the characters corresponding to letters above are reserved.

So for example, is U+1D538, is U+1D539, but U+1D53A is reserved and you must use (U+2102) instead.

One letter not mentioned above is (U+2119). It has HTML entities ℙ and ℙ.

So the double-struck versions of C, H, N, P, Q, R, and Z are down in the BMP (Basic Multilingual Plane) and the rest are in the SMP (Supplementary Multilingual Plane). I suspect characters in the SMP are less likely to have font support, but that may not be a problem.

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