java do notation example

Simple example for https://github.com/josejuan/lombok a lombok fork with bind and BindTo extensions to support "Java do notation".

quick class descriptions

• Either, typical monad.
• MOption, the Java 8 Option monad wrapper to support BindTo.
• MStream, the Java 8 Stream monad wrapper to support BindTo.
• Parser, utility methods.
• Tuple, for anonymous data types.
• main, the example.

example

The example read lazily one (potentially big) file with quadratic equations like:

A x^2 + B x + C

Multiple equations for each line is valid separating equations by ;.

The process compute only real equation roots.

The process write the valid result or one error with line and equation number if parsing or complex number as result is given.

The process consume a constant amount of memory (no matter how big is the input file).

configuration

On build.gradle file you should configure the path to the lombok with java-do-notation.

example runs

I created seven equations files, the file equations.7z contains random instances for 10^1, 10^2, ... and 10^5 lines (each line with 5 average equations).

$ wc -l t[1-7].equations
        10 t1.equations
       100 t2.equations
      1000 t3.equations
     10000 t4.equations
    100000 t5.equations
   1000000 t6.equations
  10000000 t7.equations

$ for i in `seq 1 7`; do echo -n "$i: "; time -f "%E, %M" java -Xms40m -Xmx40m -jar ./build/libs/do-notation-example.jar ~/tmp/t$i.equations ~/tmp/t$i.results; done
1: 0:00.20, 36252
2: 0:00.33, 42508
3: 0:00.57, 65704
4: 0:01.37, 91480
5: 0:05.65, 96380
6: 0:46.65, 103404
7: 7:36.11, 106860