The NG Programming Language

Grammar

This document describes the syntax of ng language.

1. Declarations

ng programs consist of declarations including:

[Module]:
   [ModuleDeclaration]
   [UseDeclaration]
   [ExportDeclaration]
   [FunctionDeclaration]
   [ValueDeclaration]

1.1 Module and use declaration

Module declaration is used to specify a module name for current compilation unit. Module name is separated by DOT (.), module name can also be a string literal if it is a keyword.

[ModuleDeclaration]:
   module [ModuleName];
[ModuleName]:
   [StringLiteral]
   [Identifier]
   [Identifier].[ModuleName]
   [StringLiteral].[ModuleName]

Use declaration is to import symbols from module

[UseDeclaration]:
    use [ModuleName];
    use [ModuleName].*;
    use [ModuleName].[Identifier];

1.2 Export declaration

Export declaration is to specify which symbols are exposed to other modules.

[ExportDeclaration]:
    export [Identifier] ";"
    export "{"[Identifier] ("," [Identifier])* "}"

1.3 Function declaration

Function declaration is to declare or define a function inside a module.

[FunctionDeclaration]:
    fun [FunctionSignature]
    fun [FunctionSignature] [FunctionBody]

[FunctionSignature]:
    [FunctionName] "(" ([FunctionParameter] ("," [FunctionParameter])* )? ")"

[FunctionName]:
    [Identifier]

[FunctionParameter]:
    [Identifier] ":" [Type]

[FunctionBody]:
    [Statement]

1.4 Value declaration

Value declaration is to define variables inside a module or a function

[ValueDeclaration]:
    val [Identifier] (":" [Type])? "=" [Expression]

2. Statements

Statement is basic execution unit of ng, and it is assured that statement must execute in sequential order.

Value declaration is a special case because it is also treat like a statement inside function.

[Statement]:
    [SimpleStatement]
    [CompoundStatement]
    [IfStatement]
    [ReturnStatement]
    [ValueDeclaration]

2.1 Simple statement and Compound statement

Simple statement is literally an expression with a semicolon(;) at the end.

Compound statement is a couple of statements grouped in a curly-brace pair({})

[SimpleStatement]:
    [Expression] ";"

[CompoundStatement]:
    "{"  [Statement]*  "}"

2.2 Conditional statements

if and case are basic conditional statements using conditional expression or pattern matching.

[IfStatement]:
    if "(" [Expression] ")" [Statement]
    if "(" [Expression] ")" [Statement] else [Statement]

2.3 Jump statements

ng has few jump statement to implement advanced control flow:

• return
• continue
• break
• yield (in design)

[ReturnStatement]:
    return [Expression] ";"
    "=>" [Expression] ";"

3. Expression

Expression is used to describe the calculations and function calls in ng to perform actual program logic.

``` [Expression]: [PrimaryExpression] [FunCallExpression] [IdAccessorExpression] [BinaryExpression] [NewObjectExpression]

[NewObjectExpression]: new [TypeName] “{“ ([PropertyAssignment] “,”)* [PropertyAssignment] “}”

[PropertyAssignment]: [Identifier] “:” [Expression]

[TypeDeclaration]: type [TypeName] “{“ ([PropertyDeclaration] “;”)* ([MethodDeclaration] “;”)* “}”

[PropertyDeclaration]: property [Identifier]

[MethodDeclaration]: fun [MethodName] “(“ ([FunctionParameter] (“,” [FunctionParameter])* “)” [FunctionBody]

[PrimaryExpression]: [Identifier] [Literals] [FunCallExpression]: [Expression]”(“ [Expression]* “)”

[IdAccessorExpression]: [Expression].[Identifier] [Expression].”(“ [Expression] “)”

[BinaryExpression]: [Expression] [Operator] [Expression]