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Project review: JGibberish

Project review: JGibberish. By: Jake Tenberg & Chelsea Shipp. Basic syntax. Types: Integers: 6, 5 Strings: [HelloWorld] Functions: <~name,?(param1),body> Function call: @name@ Variable declaration: (param1,value) Variable reference/call: #param1# Enode and Fnode

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Project review: JGibberish

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  1. Project review: JGibberish By: Jake Tenberg & Chelsea Shipp

  2. Basic syntax • Types: • Integers: 6, 5 • Strings: [HelloWorld] • Functions: <~name,?(param1),body> • Function call: • @name@ • Variable declaration: • (param1,value) • Variable reference/call: • #param1# • Enode and Fnode • Single characters “e” and “f” • Execution node • ^

  3. Concepts implemented

  4. Concepts implemented (listed) • Token • Terminal • Non-terminal • Lexical analysis • Syntactic analysis • BNF • Parse tree • Abstract syntax • Abstract syntax tree • Interpretation • Substitution • Variables • Static and dynamic scoping • Types • Type system • Static and dynamic typing • Functions • Parameters and arguments • Parameter passing • Activation records • Runtime stack • First-class functions • Recursion

  5. Project requirements • Substitution -- ✔ • First-class functions -- ✔ • Static scoping with dynamic scoping if appropriate -- ✔ • Static or dynamic typing -- ✔ • Interpretation of an abstract syntax tree -- ✔

  6. Substitution • Implemented through use of a variable table. • When a function is called, the old variable table is pushed onto the runtime stack. • Loop through the function’s parameters and get the values for those variables from the internal stack. These name and value pairs are put into the variable table. • After the function is run, pop the old variable table off of the runtime stack.

  7. First-class functions • As seen in FirstClassMeows.gib (example file included in the project), functions can be passed as parameters to other functions. • They are handled just like other variables • Pushed onto the internal stack and popped off when needed

  8. Static scoping • Every time a variable is encountered, it is added to the variable table. • When a function is encountered: • Old variable table pushed onto runtime stack • Parameters from the function are substituted with values popped from the stack • These values are then added/changed in the variable table • After the function finishes executing, the variable table is replaced with the one popped from the runtime stack • This ensures that the same named variables have different values in different scopes

  9. Static/Dynamic typing • Mainly dynamically typed • We throw exceptions at runtime if things aren’t the type we want (e.g. value instanceof String) • However, the types are defined when things are declared (the syntax for declaration) • Strings: enclosed in brackets • Integers: plain numbers • Functions: enclosed in angle brackets with special syntax distinguishing the name and parameters from the body • In addition, Java is statically typed

  10. Interpretation of abstract syntax tree • Example AST of Double.gib (given a number in the program, outputs two times that number)

  11. Output of runtime stack • Example runtime stack of FirstClassMeows.gib

  12. Some example programs • HelloWorld.gib : simple Hello World program. Good introduction to Gibberish syntax. • FirstClassMeows.gib : uses first-class functions to output a series of meows. • expGib.gib : uses variables “g” and “v”, which represent numbers, and compute g^v recursively. • fibGib.gib : gets the given term of the Fibonacci. • scopeGib.gib : shows static scoping! The value of the variable “a” changes depending on the scope. • It has different values based on which function is being called.

  13. Improvements for the future • Allow more types • Right now we allow Strings, Integers (including multiple digits), and functions. • Possible inclusions: doubles, booleans, arrays • Allow the program to pass in parameters • e.g. instead of hardcoding a value to find the Fibonacci number of, allow the user to pass in a value on the command line. • SQL commands • We tried to implement a few basic commands • Better way of implementing errors, rather than just runtime exceptions

  14. Cool features • Theoretically infinite instruction sets • Only limited by the size of an integer in java (2^32) • The fifth instruction set is meows! • We fully implemented the Gibberish language, from scratch • Our implementation has features like static scoping, variables, and functions that other implementations don’t have • Optional flags to toggle the following options: • Seeing abstract syntax tree, runtime stack • Not seeing output

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