asg0451/haskshell

Nascent shell/interpreter written in Haskell

About

Happy

• Happy is a parser generator for haskell. like yacc/bison is for C.
• its lexer equivalent is called Alex, which i just implemented use of
• install happy and alex using:

  stack install happy alex
      

  these will probably be installed when you run stack install, but I’m not really sure.

Requirements

• This program requires stack to install dependencies and compile properly.
• ghc and cabal can be install using pacman on arch, probably apt-get on ubuntu or whatever.
• stack can be installed idk from the website or whatever
• otherwise stack will take care of libraries when you run the command stack install

Building

• just run

  stack install
      

Remember

To install libraries manually, run

stack install <package>

Running

stack will install binaries into $HOME/.local/bin, so add this to your path if you want

TODOs

• [X] switch from system.posix.process to system.process, for return val and pipe support
  • hopefully this will fix the order of execution of commands not being guaranteeable, i.e. not forked
• [X] problem – varRef vs single word commands. possible solution:
  • make if-stmts only contain exprs if theyre wrapped in brackets of some sort
• [X] think about ambiguity, e.g. ‘if 1 == 2 then echo hi ; a = 2’ gets parsed as ‘if .. then ( echo hi ; a = 2)’
  • edit %left precedence accordingly
• [X] find a better way to handle empty lines
• [X] start using alex. adding ‘==’ support broke assignment without spaces
• [ ] seperate Expression datatype into Expression and Literal?
• [X] make variable evaluation explicit
• [ ] other things that are listed throughout the code