As I’ve been reporting in recent entries, I’ve been working with a symbolic logic course which has been using various exotic symbols including double struck P (ℙ). Since every Unicode point seems to have its own story, I thought I would report some of the ineresting challenges for this character.
Finding It
When you are discussing a topic with lots of different symbols, you soon realize that in terms of Unicode, they will come from multiple blocks. For instance double struck P is from the Letter Like Symbols block (starts at U+2100), while other math symbols may be in Arrows block, the Number Forms block, the Mathematical Operators Block or possibly the Dingbats Block. You can see from the Unicode Org Symbols and Punctuation Chart just how many blocks are involved.
Although a user doesn’t normally have to know the Unicode point value, because many insertion tools such as the Windows Character Map, Mac Character Pallete or others are organized primarily by block, you do have to sort of have an idea of how blocks work.
Rarity
Fonts with a robust set of math symbols are still pretty rare, and sometimes the letter like symbols are even rarer. At one point I had ℙ (P) pulling from one font and ℚ (Q) from another…interesting. Below are some fonts I know have doublestruck letters like ℙ,ℚ.
- Windows/Mac Leopard – Arial Unicode MS
- Macintosh OS X – Apple Symbol, Hiragino Mincho Pro W3 (Japanese), Hiragino Mincho Pro W6 (Japanese ), Lucida Sans
- Unicode Symbols
- Hindsight Unicode
- Chrysanthi (Chryʃsanþi)
Formatting Issues
Normally I try to avoid font and size specifications, but double struck P is an interesting counterexample. One challenge is that because the legs are hollowed out, it has a much lighter visual appearance than say normal P. My base text is 12 px on the Web, but for the double struck P, I decided to bump up the size to about 16 px (in a standards-compliant way of 1.3 em).
The other issue was selecting font faces. I wanted one with thick double legs – if you look at the font chart below from my Mac, you’ll see that some fonts had some very skinny legs.
I also prefer the serif fonts in this case since I personally believe serifs help inexperieced users in reading unfamiliar scripts (in this case undergraduate college students). For this course, I’ll probably point students to some freeware fonts I like
