gachapy.keylang

The tokenizer, parser, and interpreter for KeyLang, the language used by gachapy to save and load custom rarity to drop rate functions KeyLang is a simple calculator-based language. Each token in the language must be separated by a space. The expressions follow standard order of operations. The following are allowed operations: + : addition - : subtraction * : multiplication / : division ^ : exponent ( … ) : parentheses (for overriding order of operations), where … is any expression any float literal R : rarity, to be substituted upon interpretation time

KeyLang Grammar

Expr -> Term + Expr | Term - Expr | Term Term -> Factor * Term | Factor / Term | Factor Factor -> Base ^ Factor | Base Base -> Const | ( Expr ) Const -> <float literal> | <rarity> Rar -> <rarity>

Example: 2 * ( 1 + R ) / 5 ^ 2 where R = rarity

Author: Jacob Kerr, 2021

Module Contents

Classes

Ast	The base class of the abstract syntax tree
_Expr	An expression in the KeyLang grammar
_Term	A term in the KeyLang grammar
_Factor	A factor in the KeyLang grammar
_Float	A float literal in the KeyLang grammar
_Rar	A rarity variable in the KeyLang grammar

Functions

parse(→ Ast)	Parses the inputed KeyLang expression into a KeyLang abstract syntax
_tokenize(→ List[str])	Converts the inputed KeyLang expression into a list of tokens
_parse_tokens(→ Ast)	Parses the inputted tokens into a KeyLang abstract syntax tree
_parse_expr(→ Ast)	Parses the inputted tokens as an expression
_parse_term(→ Ast)	Parses the inputted tokens as a term
_parse_factor(→ Ast)	Parses the inputted tokens as a factor
_parse_base(→ Ast)	Parses the inputted tokens as a base
_parse_const(→ Ast)	Parses the inputted tokens as a constant
interpret(→ float)	Evaluates the KeyLang AST to a value using the rarity

exception gachapy.keylang.SyntaxError

Bases: BaseException

The exception thrown when a syntax error is found

class gachapy.keylang.Ast(left=None, right=None, data=None)

Bases: object

The base class of the abstract syntax tree

class gachapy.keylang._Expr(left=None, right=None, data=None)

Bases: Ast

An expression in the KeyLang grammar

__str__() → str

Return str(self).

class gachapy.keylang._Term(left=None, right=None, data=None)

Bases: Ast

A term in the KeyLang grammar

__str__() → str

Return str(self).

class gachapy.keylang._Factor(left=None, right=None, data=None)

Bases: Ast

A factor in the KeyLang grammar

__str__() → str

Return str(self).

class gachapy.keylang._Float(left=None, right=None, data=None)

Bases: Ast

A float literal in the KeyLang grammar

__str__() → str

Return str(self).

class gachapy.keylang._Rar(left=None, right=None, data=None)

Bases: Ast

A rarity variable in the KeyLang grammar

__str__() → str

Return str(self).

gachapy.keylang.parse(s: str) → Ast

Parses the inputed KeyLang expression into a KeyLang abstract syntax tree

Parameters

sstr

the expression to parse

Returns

Ast

the KeyLang AST representative of the expression

gachapy.keylang._tokenize(s: str) → List[str]

Converts the inputed KeyLang expression into a list of tokens

Parameters

sstr

the KeyLang expression to tokenize

Returns

List[str]

the list of tokens

gachapy.keylang._parse_tokens(tokens: List[str]) → Ast

Parses the inputted tokens into a KeyLang abstract syntax tree

Parameters

tokensList[str]

the list of tokens to parse

Returns

Ast

the abstract syntax tree representative of the tokens

gachapy.keylang._parse_expr(tokens: List[str]) → Ast

Parses the inputted tokens as an expression

Parameters

tokensList[str]

the list of tokens to parse

Returns

Ast

the abstract syntax tree representative of the expression

gachapy.keylang._parse_term(tokens: List[str]) → Ast

Parses the inputted tokens as a term

Parameters

tokensList[str]

the list of tokens to parse

Returns

Ast

the abstract syntax tree representative of the term

gachapy.keylang._parse_factor(tokens: List[str]) → Ast

Parses the inputted tokens as a factor

Parameters

tokensList[str]

the list of tokens to parse

Returns

Ast

the abstract syntax tree representative of the factor

gachapy.keylang._parse_base(tokens: List[str]) → Ast

Parses the inputted tokens as a base

Parameters

tokensList[str]

the list of tokens to parse

Returns

Ast

the abstract syntax tree representative of the base

gachapy.keylang._parse_const(tokens: str) → Ast

Parses the inputted tokens as a constant

Parameters

tokensList[str]

the list of tokens to parse

Returns

Ast

the abstract syntax tree representative of the constant

gachapy.keylang.interpret(ast: Ast, rarity: float) → float

Evaluates the KeyLang AST to a value using the rarity

Parameters

astAst

the AST of the expression

rarityfloat

the value for the rarity

Returns

float

the result of the expression