pPanda-beta/kalkulator

A kotlin based extensible calculator

A kotlin based extensible calculator

Mentions

• The execution mechanism is highly influenced by my work presto-utils
• The visitor pattern is inspired by trino-parser
• Some part of it uses Shunting-yard algorithm

For users

How to run ?

Directly :

./gradlew ':kalkulator-cli:run' --args="  -e '5*4 + 3/2' "

OR

Build and then run

./gradlew clean shadowJar 
java -jar ./kalkulator-cli/build/libs/kalkulator-cli-*-all.jar -e '5*4 + 3/2'

For developers

How to implement a new operator?

1. Create a token pattern e.g. val MODULO_TOK = PatternBasedTokenType.fromString("MODULO", "%")
2. Create an operator

   val MODULO = BinaryOperator(MODULO_TOK, Associativity.LEFT_TO_RIGHT)

3. Create an operator module to add precedence and evaluation code

   newModule(MODULO, MULT_DIV_PRECEDENCE, Double::mod)

   Check more at StandardOperatorModules

How to implement a ternary operator?

Well since we are not using any parser generator like antlr4 or lark it is hard to introduce a new grammar rule. The following components need to be modified

• Parser (maybe lexer as well)
• AstVisitor
• ExpressionEvaluator (as a sub class of AstVisitor)

TODO

1. Try to make parenthesis as a first class unary operator
2. Re-implement expression-parser using a parser generator like antlr4 or lark