8 ms·

Subscripts and superscripts are probably some of my most-used unicode identifiers. Supported in Julia but not Python 3. In [1]: α₁ = 1 File "<ipytho

by 3JPLW 7y ago

Subscripts and superscripts are probably some of my most-used unicode identifiers. Supported in Julia but not Python 3. In [1]: α₁ = 1 File "<ipython-input-1-3c2973844bb9>", line 1 α₁ = 1 ^ SyntaxError: invalid character in identifier

diminoten 7y ago
Inline? I dunno, shouldn't the thinking be separated from the showing? IOW, of course python can display sub/superscript, but using it in the code doesn't feel necessary.
- 3JPLW 7y ago
  Yes, absolutely "inline" as identifiers in your code. So many algorithms use subscript or superscript notations, and it's so nice to be able to use names like vₓ or H₀ or χ² or Aᵀ directly.
  - jacobolus 7y ago
    Nice as long as you are only reading a paper printout of the code and never have to write or edit it yourself, since your keyboard is never going to be set up for typing someone else’s choice of weird symbols.
    - 3JPLW 7y ago
      That's also not true. Julia itself defines the tab completions for all these characters — and they'll be very familiar to you if you've ever used latex. They're just a tab away in every editor worth its salt. α₁ \alpha<TAB>\_1<TAB> vₓ v\_x<TAB> H₀ H\_0<TAB> χ² \chi<TAB>\^2<TAB> Aᵀ A\^T<TAB> When I went to do the python demo above, IPython also tab-completed the `\alpha` above... but to get the ₁ the quickest and easiest way for me to get it was in my Julia editor.
      - jacobolus 7y ago
        So now anyone who might want to work with your program has to be trained in LaTeX and the Greek alphabet, and has to use a specialized IDE/editor. Fair enough in some contexts, but I don’t find that to be the nicest general-audience feature. YMMV.
        3JPLW 7y ago
        Folks who want to work with my program are going to know Julia. These tab completions aren't limited to editors/IDEs, they also work at the REPL. Just copy-paste the character you didn't know into Julia's help prompt: help?> α "α" can be typed by \alpha<tab> Code is for reading much more than writing — especially for a new person. I maintain that matching the canonical form of the algorithm I'm implementing will help them gain their feet faster. Good example: https://github.com/JuliaStats/Distances.jl/blob/c21aab0fae30916354bc104108c1c065eeb0c6aa/src/haversine.jl#L30-L33 https://github.com/JuliaStats/Distances.jl/blob/c21aab0fae30... vs. https://www.npmjs.com/package/haversine-geolocation#introduction https://www.npmjs.com/package/haversine-geolocation#introduc... (note the mathematical formula on that page and the JS code compared to Julia's)
        jacobolus 7y ago
        The use of λ₁ and φ₂ instead of l1 and a2 or x1 and y2 or longitude1 and latitude2 is cute, but really not that big a practical improvement. Sure someone can pattern-match the code to the already-derived line in a reference book somewhere, but that doesn’t help at all with reasoning about the geometrical relationships or developing new algorithms, following control flow, building abstractions, improving precision, handling edge cases, ... It’s mostly helpful when you want to treat your formulas as an externally defined black box. * * * Aside: The problem in this particular example is that spherical coordinates and spherical trigonometry are just not a very good formalism for calculating anything, in either theory or practice. Unfortunately cartography, geodesy, etc. are bound by tradition and there hasn’t been much effort to switch them to better tools. I’ve been trying to read a spherical trigonometry textbook (Todhunter, 1878) the last few days and following along is a huge pain. Much better is to switch to cartesian coordinates or stereographically projected coordinates, and then use vector methods (and skip writing explicit coordinates in your code to the extent possible). All of the proofs and derivations get nicer, with geometrically meaningful steps and conclusions. Now your points can just be called p and q or a and b (or if you have a lot of them and aren’t pressed for space in each expression, points[i] and points[i+1]), and the coordinates stay internal. In addition to using clearer code, the calculations will also be faster, more precise, with better numerical stability, take up less memory/bandwidth, ... Here’s some general math for an arbitrary-dimensional sphere; for just the 2-sphere everything is simpler. http://geocalc.clas.asu.edu/pdf/CompGeom-ch3.pdf http://geocalc.clas.asu.edu/pdf/CompGeom-ch3.pdf
Skunkleton 7y ago
Out of curiosity, how do you physically enter these subscripts? It seems a standard keyboard would be somewhat limiting.
- 3JPLW 7y ago
  It's just a simple tab completion in the REPL and usual editors, see: https://news.ycombinator.com/item?id=20346931 https://news.ycombinator.com/item?id=20346931
alanbernstein 7y ago
Why do you prefer using subscripts rather than simple ASCII numerals in variable names?
- 3JPLW 7y ago
  It's not a big thing, and obviously it's a matter of taste, but I find it improves readability slightly. It's most notable if I'm doing work based on literature with standard notations (e.g., α₀ instead of alpha_0), but it can also be really nice to help keep track of different states of the same value, e.g., loc₀ vs. locᵢ and locₖ inside loop(s) or with staggered indexing computations.

by 3JPLW 7y ago

diminoten 7y ago

Inline? I dunno, shouldn't the thinking be separated from the showing? IOW, of course python can display sub/superscript, but using it in the code doesn't feel necessary.

3JPLW 7y ago
Yes, absolutely "inline" as identifiers in your code. So many algorithms use subscript or superscript notations, and it's so nice to be able to use names like vₓ or H₀ or χ² or Aᵀ directly.
- jacobolus 7y ago
  Nice as long as you are only reading a paper printout of the code and never have to write or edit it yourself, since your keyboard is never going to be set up for typing someone else’s choice of weird symbols.
  - 3JPLW 7y ago
    That's also not true. Julia itself defines the tab completions for all these characters — and they'll be very familiar to you if you've ever used latex. They're just a tab away in every editor worth its salt. α₁ \alpha<TAB>\_1<TAB> vₓ v\_x<TAB> H₀ H\_0<TAB> χ² \chi<TAB>\^2<TAB> Aᵀ A\^T<TAB> When I went to do the python demo above, IPython also tab-completed the `\alpha` above... but to get the ₁ the quickest and easiest way for me to get it was in my Julia editor.
    - jacobolus 7y ago
      So now anyone who might want to work with your program has to be trained in LaTeX and the Greek alphabet, and has to use a specialized IDE/editor. Fair enough in some contexts, but I don’t find that to be the nicest general-audience feature. YMMV.
      - 3JPLW 7y ago
        Folks who want to work with my program are going to know Julia. These tab completions aren't limited to editors/IDEs, they also work at the REPL. Just copy-paste the character you didn't know into Julia's help prompt: help?> α "α" can be typed by \alpha<tab> Code is for reading much more than writing — especially for a new person. I maintain that matching the canonical form of the algorithm I'm implementing will help them gain their feet faster. Good example: https://github.com/JuliaStats/Distances.jl/blob/c21aab0fae30916354bc104108c1c065eeb0c6aa/src/haversine.jl#L30-L33 https://github.com/JuliaStats/Distances.jl/blob/c21aab0fae30... vs. https://www.npmjs.com/package/haversine-geolocation#introduction https://www.npmjs.com/package/haversine-geolocation#introduc... (note the mathematical formula on that page and the JS code compared to Julia's)
        jacobolus 7y ago
        The use of λ₁ and φ₂ instead of l1 and a2 or x1 and y2 or longitude1 and latitude2 is cute, but really not that big a practical improvement. Sure someone can pattern-match the code to the already-derived line in a reference book somewhere, but that doesn’t help at all with reasoning about the geometrical relationships or developing new algorithms, following control flow, building abstractions, improving precision, handling edge cases, ... It’s mostly helpful when you want to treat your formulas as an externally defined black box. * * * Aside: The problem in this particular example is that spherical coordinates and spherical trigonometry are just not a very good formalism for calculating anything, in either theory or practice. Unfortunately cartography, geodesy, etc. are bound by tradition and there hasn’t been much effort to switch them to better tools. I’ve been trying to read a spherical trigonometry textbook (Todhunter, 1878) the last few days and following along is a huge pain. Much better is to switch to cartesian coordinates or stereographically projected coordinates, and then use vector methods (and skip writing explicit coordinates in your code to the extent possible). All of the proofs and derivations get nicer, with geometrically meaningful steps and conclusions. Now your points can just be called p and q or a and b (or if you have a lot of them and aren’t pressed for space in each expression, points[i] and points[i+1]), and the coordinates stay internal. In addition to using clearer code, the calculations will also be faster, more precise, with better numerical stability, take up less memory/bandwidth, ... Here’s some general math for an arbitrary-dimensional sphere; for just the 2-sphere everything is simpler. http://geocalc.clas.asu.edu/pdf/CompGeom-ch3.pdf http://geocalc.clas.asu.edu/pdf/CompGeom-ch3.pdf

Skunkleton 7y ago

Out of curiosity, how do you physically enter these subscripts? It seems a standard keyboard would be somewhat limiting.

3JPLW 7y ago
It's just a simple tab completion in the REPL and usual editors, see: https://news.ycombinator.com/item?id=20346931 https://news.ycombinator.com/item?id=20346931

alanbernstein 7y ago

Why do you prefer using subscripts rather than simple ASCII numerals in variable names?

3JPLW 7y ago
It's not a big thing, and obviously it's a matter of taste, but I find it improves readability slightly. It's most notable if I'm doing work based on literature with standard notations (e.g., α₀ instead of alpha_0), but it can also be really nice to help keep track of different states of the same value, e.g., loc₀ vs. locᵢ and locₖ inside loop(s) or with staggered indexing computations.