Libra

Libra a python based programming language

Documentation

• Shell.py: It will read the raw input from the terminal and display it.

• Libra.py: Holds all the code of language.

o Error class: It handles all the error and display it to the user.

 It returns a string/error which tells path of file in which error occurred, type of error and from which it occurs and line no. in which an error occurred.

o Position class: It tells index, column, line etc

 Advance(): It moves the execution/Cursor to next character.

o Lexer class: It will go through input character by character and break them into list of tokens.

 Make_tokens():It checks that the character is of which token type(=,-,*,/) and append it in tokens list(use else-if ladders).

 Make_number(): It takes raw input and specify int or float and make it in integer format.

 Ex:- Libra > 2 + 2 [INT:2, PLUS, INT:2] Libra > 2.52.5 [FLOAT:2.5, MUL, FLOAT:2.5] Libra > 77 d Illegal Character: 'd'

o Nodes: It tells us about factor, binary ops and unary ops

 NumberNode: It works on factor.

 BinOpNode: It works on binary operators

 UnaryOpNode: It woks on Unary operators.

o ParseResult class: It returns the AST(Abstract Syntax Tree) which is created by parse the expression.

o Parser class: It recursively checks for expression, term and factor and parse it.

o Interpreter class: It runs and helps to get the desired result.

• grammar.txt: It specifies grammar which we used to parse the expressions or to write code.

• Strings_with_arrows.py: It helps to obtain where the error is came from.

• Power operator-> ‘^’

• [new]Modulo operator-> ‘%’

• Variable syntax: KEYWORD IDENTIFIER =

Var a = 5

• Conditional Statements : if,elsif,else

• From loop(for): KEYWORD:from IDENTIFIER EQ expr KEYWORD:to expr

(KEYWORD:step expr)? KEYWORD:then expr

• Until loop(while) : KEYWORD:until expr KEYWORD:then expr

• Continue: cont

• Break: brk

• Comments : !! !!

• len(): To get the length

• exec(): to run the program file