5 ms·

I think it's a lot easier to understand what some code does if you don't have to read a lot of language imposed cruft that surrounds the actual 'meat' of the al

by yariv 18y ago

I think it's a lot easier to understand what some code does if you don't have to read a lot of language imposed cruft that surrounds the actual 'meat' of the algorithm. Erlang really is easier than Java -- both to read and to write. I think people too often confuse "different" with "difficult".

anamax 18y ago
I wasn't thinking Java. I was thinking lisp or python.
- silentbicycle 18y ago
  For one thing, the pattern matching used in Erlang, ML, and Haskell can be quite easy to read. For example, something like let days_in_month m = match m with | Jan | Mar | May | Jul | Aug | Oct | Dec -> 31 | Apr | Jun | Sept | Nov -> 30 | Feb -> if leap_year () then 29 else 28 It takes a small amount of context (all "| Val" sections without a -> ... side match together), but it's a pretty direct correspondence.
  - nostrademons 18y ago
    That's not much harder in C or Java, given appropriate enum declarations: public int days_in_month(month) { switch(month) { case JAN: case MAR: case MAY: case JUL: case AUG: case OCT: case DEC: return 31 case APR: case JUN: case SEPT: case NOV: return 30; case FEB: if(leap_year()) return 29; else return 28; } } Pattern-matching really shines when you need to destructure the argument, then do something similar to the result regardless of which case resulted in the destructuring. For example, compare red-black trees written in Java: http://www.docjar.com/html/api/java/util/TreeMap.java.html http://www.docjar.com/html/api/java/util/TreeMap.java.html vs. those written in Haskell: http://www.cse.unsw.edu.au/~dons/data/RedBlackTree.html http://www.cse.unsw.edu.au/~dons/data/RedBlackTree.html The rebalancing code in Java is 80 lines long. The rebalancing code in Haskell is 6.
    - silentbicycle 18y ago
      I couldn't think of a better example at the time. Something that simultaneously matched several fields (whether destructured from one variable or not) and/or had guards would be a better example. Maybe something like this (in pseudo-ML): (* Look up order code for a Sci-Fi GadgetTM, units are in cm *) let gadget_order_code width depth height color has_laser = match (width depth height color has_laser) = (* The original, simple code *) | 5, 2, 1, Red, true -> "ZAP-X" (* Most common width, color *) | 4, d, h, Blue, true -> sprintf "ZAP-4-%d%d+" (str d) (str h) "+" (* C for Custom Color *) | 4, d, h, c, false -> "ZAP-4C-%d%d-%c" (str d) (str h) (color_code c) (* Orange lasers are discontinued *) | w, d, h, c, true when (w + d + h) < 15 and c != Orange -> "ZAP-S-%d%d%d-%c" (str w) (str d) (str h) (color_code c) | _, _, _, _, _ -> failwith "Unavailable" That's a little complicated to determine with pattern matching or via a database, but doing it in a series of nested if statements would get mind boggling.
      - silentbicycle 18y ago
        (oops. lost the sprintfs...)

by yariv 18y ago

anamax 18y ago

I wasn't thinking Java. I was thinking lisp or python.

silentbicycle 18y ago
For one thing, the pattern matching used in Erlang, ML, and Haskell can be quite easy to read. For example, something like let days_in_month m = match m with | Jan | Mar | May | Jul | Aug | Oct | Dec -> 31 | Apr | Jun | Sept | Nov -> 30 | Feb -> if leap_year () then 29 else 28 It takes a small amount of context (all "| Val" sections without a -> ... side match together), but it's a pretty direct correspondence.
- nostrademons 18y ago
  That's not much harder in C or Java, given appropriate enum declarations: public int days_in_month(month) { switch(month) { case JAN: case MAR: case MAY: case JUL: case AUG: case OCT: case DEC: return 31 case APR: case JUN: case SEPT: case NOV: return 30; case FEB: if(leap_year()) return 29; else return 28; } } Pattern-matching really shines when you need to destructure the argument, then do something similar to the result regardless of which case resulted in the destructuring. For example, compare red-black trees written in Java: http://www.docjar.com/html/api/java/util/TreeMap.java.html http://www.docjar.com/html/api/java/util/TreeMap.java.html vs. those written in Haskell: http://www.cse.unsw.edu.au/~dons/data/RedBlackTree.html http://www.cse.unsw.edu.au/~dons/data/RedBlackTree.html The rebalancing code in Java is 80 lines long. The rebalancing code in Haskell is 6.
  - silentbicycle 18y ago
    I couldn't think of a better example at the time. Something that simultaneously matched several fields (whether destructured from one variable or not) and/or had guards would be a better example. Maybe something like this (in pseudo-ML): (* Look up order code for a Sci-Fi GadgetTM, units are in cm *) let gadget_order_code width depth height color has_laser = match (width depth height color has_laser) = (* The original, simple code *) | 5, 2, 1, Red, true -> "ZAP-X" (* Most common width, color *) | 4, d, h, Blue, true -> sprintf "ZAP-4-%d%d+" (str d) (str h) "+" (* C for Custom Color *) | 4, d, h, c, false -> "ZAP-4C-%d%d-%c" (str d) (str h) (color_code c) (* Orange lasers are discontinued *) | w, d, h, c, true when (w + d + h) < 15 and c != Orange -> "ZAP-S-%d%d%d-%c" (str w) (str d) (str h) (color_code c) | _, _, _, _, _ -> failwith "Unavailable" That's a little complicated to determine with pattern matching or via a database, but doing it in a series of nested if statements would get mind boggling.
    - silentbicycle 18y ago
      (oops. lost the sprintfs...)