README.md

INSRUCTIONS TO RUN

1. unzip galaxy.zip
2. cd galaxy/
3. ant
4. java -cp galaxy.jar com.galaxy.GalaxyApp <path to input file>

PROGRAM DESIGN

1. class design

    |- Symbol
        |- GalaxySymbol
        |- RomanSymbol
    |- Number
        |- GalaxyNumber
        |- RomanNumber
    |- NumberBuilder
        |- GalaxyNumberBuilder
        |- RomanNumberBuilder
    |- NumberParser
        |- BaseNumberParser
    |- ParseRule
        |- BaseDisjunctiveRule
            |- DescendingRule
            |- RepeatableRule
            |- SubtractableRule
    |- NumberBuilderFactory
    |- GalaxyNotesParser
    |- MetalPriceCalculator
   

   • Symbol classes: symbols with the number systems; also encodes the rules for conversion btw them
   • Number classes: immutable classes for the numbers, no direct instantiation is allowed
   • NumberParser classes: generic class to encode the algorithm for parsing the numbers
   • NumberBuilder classes: generic class to build the numbers; numbers are only allowed to be created via builder
   • ParserRule classes: encodes the parsing rules; the rules can be disjunctive or conjunctive
   • NumberBuilderFactory class: factory class to create builders
   • GalaxyNotesParser class: I/O supported

2. algorithm for parsing roman numerals:

   • O(n) complexity; makes use of stack for storing intermediate results in processing loop

3. rationale behind:

   • By restricting the creation of numbers to builders, we can encapsulate rules properly for the number system
   • By restricting the creation of builders to NumberBuilderFactory, we can control the proper initialization of them
   • By using generic NumberParser classes, we are able to abstract common parsing logic for different numerals
   • By using ParseRule classes, we can use different set of rules for different numeral systems, making it easy to extend

4. more:

   • please refer to the code and documentations.