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FrontEnd Design

Work Pipe

graph LR
I(Input) -->|code string| B(Lexer&Parser)
B -->|parse tree| A(ASTBuilder)
A --> |AST| S(SemanticChecker)
S --> |Semantic Error| H(ExceptionHandler)
A --> |Scope| S
A --> |Syntax Error| H
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the semantic check contains two steps:

  • First, the ASTBuilder
    • Build the AST
    • Register all classes and functions
    • throw some Syntax Error ( also some basic Semantic Error )
    • Assign types to New
  • Second, the SemanticChecker
    • Register the others (Scope Stack)
    • Assign types to All Exp Nodes
    • Semantic check, throw Semantic Error

This is because Mx* should implement the forwarding reference of classes and global functions.

AST Design

Node Pack

A Node usually contains

  • CodePos used in throw Exception. All Nodes.

  • Scope used to manage namespace. The following nodes have scopes attached to them.

    • RootNode
    • ForStmtNode
    • WhileStmtNode
    • IfStmtNode (This one have two scopes: ifTrue, else)
    • SuiteNode

    And the visitor will pull the scope into the scope stack when they meeting a node with Scope.

    The following two Node types contains Registry with Scope:

    • ClassDefNode
    • FuncDefNode (Parameters)

  • Registry Only in "Def" Type Node.

    A Registry records the information need in define a variable/func/class, recorded in Scope to do semantic check.

  • <some son Nodes>

    vary from different Nodes.

  • <some must information>

    enum type or integer etc.

Node List

  • BaseNode

  • RootNode

  • ClassDefNode

  • FuncDefNode

  • SuiteNode

  • VarDefNode

  • StmtNode/

    • StmtBaseNode

    • IfStmtNode

    • ForStmtNode

    • WhileStmtNode

    • ReturnStmtNode

    • ControlStmtNode

    • VarDefStmtNode

    • PureStmtNode

  • ExpNode/

  • ExpBaseNode

    • AtomExpNode

    • FuncCallExpNode

    • IndexExpNode

    • MemberExpNode

    • NewExpNode

    • PrefixExpNode

    • PostfixExpNode

    • BinaryExpNode

    • UnaryExpNode

    • AssignNode

Type & Registry Design

Type is mainly for "match":

For class, there is no need to match; For func, match a valid func-call; For variable, match their builtin-type and dimension.

  • BaseType
  • VarType
  • FuncType

Registry is like a Object's Household Register. It records information of a declaration. (Type + name + scope)

  • BaseRegistry
  • VarRegistry
  • FuncRegistry
  • ClassRegistry

Error Design

Error, or Exception (In fact there are some difference, but I think Error is more suitable to describe this wrong.)

  • Syntax Error
    • ParseFailedError
    • MainFuncError
    • ArrayDeclarationError
    • ClassDeclarationError
  • Semantic Error
    • FuncCallError
    • FuncReturnError
    • NameError
    • ScopeError
    • TypeError
    • UndefinedBehaviourError

Scope Design

Scope, for managing a "namespace".

Provide the necessary interfaces to register a variable / function / class.

And give response to a variable / function / class call

  • BaseScope

  • GlobalScope

    Able to register: class, var, func

  • NormalScope

    Able to regiser: var

    Use in: suite

  • ClassScope

    Use in: class def

    Able to regiser: func var

  • FuncScope

    Use in: func def

  • LoopScope

    Use in: for-loop, while-loop

  • IfScope

    Use in: if, else