zig/doc/langref.md

# Language Reference

## Primitive Numeric Types:

zig          |        C equivalent    | Description
-------------|------------------------|-------------------------------
        bool |                   bool |  unsigned 1-bit integer
          i8 |                 int8_t |    signed 8-bit integer
          u8 |                uint8_t |  unsigned 8-bit integer
         i16 |                int16_t |   signed 16-bit integer
         u16 |               uint16_t | unsigned 16-bit integer
         i32 |                int32_t |   signed 32-bit integer
         u32 |               uint32_t | unsigned 32-bit integer
         i64 |                int64_t |   signed 64-bit integer
         u64 |               uint64_t | unsigned 64-bit integer
         f32 |                  float |  32-bit IEE754 floating point
         f64 |                 double |  64-bit IEE754 floating point
        f128 |            long double | 128-bit IEE754 floating point
       isize |               intptr_t |   signed pointer sized integer
       usize |              uintptr_t | unsigned pointer sized integer
     c_short |                  short | for API compatibility with C
    c_ushort |         unsigned short | for API compatibility with C
       c_int |                    int | for API compatibility with C
      c_uint |           unsigned int | for API compatibility with C
      c_long |                   long | for API compatibility with C
     c_ulong |          unsigned long | for API compatibility with C
  c_longlong |              long long | for API compatibility with C
 c_ulonglong |     unsigned long long | for API compatibility with C

## Grammar

```
Root : many(TopLevelDecl) token(EOF)

TopLevelDecl : FnDef | ExternBlock | RootExportDecl | Use | StructDecl | VariableDeclaration

VariableDeclaration : option(FnVisibleMod) (token(Var) | token(Const)) token(Symbol) (token(Eq) Expression | token(Colon) Type option(token(Eq) Expression))

StructDecl : many(Directive) token(Struct) token(Symbol) token(LBrace) many(StructField) token(RBrace)

StructField : token(Symbol) token(Colon) Type token(Comma)

Use : many(Directive) token(Use) token(String) token(Semicolon)

RootExportDecl : many(Directive) token(Export) token(Symbol) token(String) token(Semicolon)

ExternBlock : many(Directive) token(Extern) token(LBrace) many(FnDecl) token(RBrace)

FnProto : many(Directive) option(FnVisibleMod) token(Fn) token(Symbol) ParamDeclList option(token(Arrow) Type)

Directive : token(NumberSign) token(Symbol) token(LParen) token(String) token(RParen)

FnVisibleMod : token(Pub) | token(Export)

FnDecl : FnProto token(Semicolon)

FnDef : FnProto Block

ParamDeclList : token(LParen) list(ParamDecl, token(Comma)) token(RParen)

ParamDecl : token(Symbol) token(Colon) Type | token(Ellipsis)

Type : token(Symbol) | token(Unreachable) | token(Void) | PointerType | ArrayType | MaybeType | CompileTimeFnCall

CompileTimeFnCall : token(NumberSign) token(Symbol) token(LParen) Expression token(RParen)

PointerType : token(Ampersand) option(token(Const)) Type

MaybeType : token(Question) Type

ArrayType : token(LBracket) Type token(Semicolon) Expression token(RBracket)

Block : token(LBrace) list(option(Statement), token(Semicolon)) token(RBrace)

Statement : Label | VariableDeclaration token(Semicolon) | NonBlockExpression token(Semicolon) | BlockExpression

Label: token(Symbol) token(Colon)

VariableDeclaration : (token(Var) | token(Const)) token(Symbol) (token(Eq) Expression | token(Colon) Type option(token(Eq) Expression))

Expression : BlockExpression | NonBlockExpression

NonBlockExpression : ReturnExpression | AssignmentExpression | AsmExpression

AsmExpression : token(Asm) option(token(Volatile)) token(LParen) token(String) option(AsmOutput) token(RParen)

AsmOutput : token(Colon) list(AsmOutputItem, token(Comma)) option(AsmInput)

AsmInput : token(Colon) list(AsmInputItem, token(Comma)) option(AsmClobbers)

AsmOutputItem : token(LBracket) token(Symbol) token(RBracket) token(String) token(LParen) (token(Symbol) | token(Arrow) Type) token(RParen)

AsmInputItem : token(LBracket) token(Symbol) token(RBracket) token(String) token(LParen) Expression token(RParen)

AsmClobbers: token(Colon) list(token(String), token(Comma))

AssignmentExpression : BoolOrExpression AssignmentOperator BoolOrExpression | BoolOrExpression

AssignmentOperator : token(Eq) | token(TimesEq) | token(DivEq) | token(ModEq) | token(PlusEq) | token(MinusEq) | token(BitShiftLeftEq) | token(BitShiftRightEq) | token(BitAndEq) | token(BitXorEq) | token(BitOrEq) | token(BoolAndEq) | token(BoolOrEq) 

BlockExpression : IfExpression | Block | WhileExpression

WhileExpression : token(While) token(LParen) Expression token(RParen) Expression

BoolOrExpression : BoolAndExpression token(BoolOr) BoolOrExpression | BoolAndExpression

ReturnExpression : token(Return) option(Expression)

IfExpression : IfVarExpression | IfBoolExpression

IfBoolExpression : token(If) token(LParen) Expression token(RParen) Expression option(Else)

IfVarExpression : token(If) token(LParen) (token(Const) | token(Var)) token(Symbol) option(token(Colon) Type) Token(MaybeAssign) Expression token(RParen) Expression Option(Else)

Else : token(Else) Expression

BoolAndExpression : ComparisonExpression token(BoolAnd) BoolAndExpression | ComparisonExpression

ComparisonExpression : BinaryOrExpression ComparisonOperator BinaryOrExpression | BinaryOrExpression

ComparisonOperator : token(BoolEq) | token(BoolNotEq) | token(BoolLessThan) | token(BoolGreaterThan) | token(BoolLessEqual) | token(BoolGreaterEqual)

BinaryOrExpression : BinaryXorExpression token(BinOr) BinaryOrExpression | BinaryXorExpression

BinaryXorExpression : BinaryAndExpression token(BinXor) BinaryXorExpression | BinaryAndExpression

BinaryAndExpression : BitShiftExpression token(Ampersand) BinaryAndExpression | BitShiftExpression

BitShiftExpression : AdditionExpression BitShiftOperator BitShiftExpression | AdditionExpression

BitShiftOperator : token(BitShiftLeft) | token(BitShiftRight)

AdditionExpression : MultiplyExpression AdditionOperator AdditionExpression | MultiplyExpression

AdditionOperator : token(Plus) | token(Minus)

MultiplyExpression : CastExpression MultiplyOperator MultiplyExpression | CastExpression

MultiplyOperator : token(Star) | token(Slash) | token(Percent)

CastExpression : CastExpression token(as) Type | PrefixOpExpression

PrefixOpExpression : PrefixOp PrefixOpExpression | SuffixOpExpression

SuffixOpExpression : PrimaryExpression option(FnCallExpression | ArrayAccessExpression | FieldAccessExpression)

FieldAccessExpression : token(Dot) token(Symbol)

FnCallExpression : token(LParen) list(Expression, token(Comma)) token(RParen)

ArrayAccessExpression : token(LBracket) Expression token(RBracket)

PrefixOp : token(Not) | token(Dash) | token(Tilde) | (token(Ampersand) option(token(Const)))

PrimaryExpression : token(Number) | token(String) | token(CharLiteral) | KeywordLiteral | GroupedExpression | Goto | token(Break) | token(Continue) | BlockExpression | token(Symbol) | StructValueExpression

StructValueExpression : token(Type) token(LBrace) list(StructValueExpressionField, token(Comma)) token(RBrace)

StructValueExpressionField : token(Dot) token(Symbol) token(Eq) Expression

Goto: token(Goto) token(Symbol)

GroupedExpression : token(LParen) Expression token(RParen)

KeywordLiteral : token(Unreachable) | token(Void) | token(True) | token(False)
```

## Operator Precedence

```
x() x[] x.y
!x -x ~x &x &const x
as
* / %
+ -
<< >>
&
^
|
== != < > <= >=
&&
||
= *= /= %= += -= <<= >>= &= ^= |= &&= ||=
```

## Literals

### Characters and Strings

                | Example  | Characters  | Escapes        | Null Term | Type
---------------------------------------------------------------------------------
 Byte           | 'H'      | All ASCII   | Byte           | No        | u8
 UTF-8 Bytes    | "hello"  | All Unicode | Byte & Unicode | No        | [5; u8]
 UTF-8 C string | c"hello" | All Unicode | Byte & Unicode | Yes       | *const u8

### Byte Escapes

      | Name
-----------------------------------------------
 \x7F | 8-bit character code (exactly 2 digits)
 \n   | Newline
 \r   | Carriage return
 \t   | Tab
 \\   | Backslash
 \0   | Null
 \'   | Single quote
 \"   | Double quote

### Unicode Escapes

          | Name
----------------------------------------------------------
 \u{7FFF} | 24-bit Unicode character code (up to 6 digits)

### Numbers

 Number literals    | Example     | Exponentiation
--------------------------------------------------
 Decimal integer    | 98222       | N/A
 Hex integer        | 0xff        | N/A
 Octal integer      | 0o77        | N/A
 Binary integer     | 0b11110000  | N/A
 Floating-point     | 123.0E+77   | Optional
 Hex floating point | TODO        | TODO