Syntax¶
Follows the complete syntax of Céu in a BNF-like syntax:
A: non terminal (starting in uppercase)a: terminal (in bold and lowercase)`.´: terminal (non-alphanumeric characters)A ::= ...: definesAas...x y:xin sequence withyx|y:xory{x}: zero or more xs[x]: optional xLIST(x): expands tox {`,´ x} [`,´](...): groups...<...>: special informal rule
Program ::= Block
Block ::= {Stmt `;´}
Stmt ::= nothing
/* Blocks */
// Do ::=
| do [`/´(ID_int|`_´)] [`(´ [LIST(ID_int)] `)´]
Block
end
| escape [`/´ID_int] [Exp]
/* pre (top level) execution */
| pre do
Block
end
/* Storage Entities / Declarations */
// Dcls ::=
| var [`&´|`&?´] `[´ [Exp [`*´]] `]´ [`/dynamic´|`/nohold´] Type ID_int [`=´ Sources]
| pool [`&´] `[´ [Exp] `]´ Type ID_int [`=´ Sources]
| event [`&´] (Type | `(´ LIST(Type) `)´) ID_int [`=´ Sources]
| input (Type | `(´ LIST(Type) `)´) ID_ext
| output (Type | `(´ LIST([`&´] Type [ID_int]) `)´) ID_ext
[ do Block end ]
/* Event Handling */
// Await ::=
| await (ID_ext | Loc) [until Exp]
| await (WCLOCKK|WCLOCKE)
//
| await (FOREVER | pause | resume)
// Emit_Ext ::=
| emit ID_ext [`(´ [LIST(Exp|`_´)] `)´]
| emit (WCLOCKK|WCLOCKE)
//
| emit Loc [`(´ [LIST(Exp|`_´)] `)´]
| lock Loc do
Block
end
/* Conditional */
| if Exp then
Block
{ else/if Exp then
Block }
[ else
Block ]
end
/* Loops */
/* simple */
| loop [`/´Exp] do
Block
end
/* numeric iterator */
| loop [`/´Exp] (ID_int|`_´) in [Range] do
Block
end
// where
Range ::= (`[´ | `]´)
( ( Exp `->´ (Exp|`_´))
| ((Exp|`_´) `<-´ Exp ) )
(`[´ | `]´) [`,´ Exp]
/* pool iterator */
| loop [`/´Exp] (ID_int|`_´) in Loc do
Block
end
/* event iterator */
| every [(Loc | `(´ LIST(Loc|`_´) `)´) in] (ID_ext|Loc|WCLOCKK|WCLOCKE) do
Block
end
| break [`/´ID_int]
| continue [`/´ID_int]
/* Parallel Compositions */
/* parallels */
| (par | par/and | par/or) do
Block
with
Block
{ with
Block }
end
/* watching */
// Watching ::=
| watching LIST(ID_ext|Loc|WCLOCKK|WCLOCKE|Abs_Cons) do
Block
end
/* block spawn */
| spawn [`(´ [LIST(ID_int)] `)´] do
Block
end
/* Exceptions */
| throw Exp
| catch LIST(Loc) do
Block
end
/* Pause */
| pause/if (Loc|ID_ext) do
Block
end
/* Asynchronous Execution */
| await async [ `(´ LIST(Var) `)´ ] do
Block
end
// Thread ::=
| await async/thread [ `(´ LIST(Var) `)´ ] do
Block
end
| spawn async/isr `[´ LIST(Exp) `]´ [ `(´ LIST(Var) `)´ ] do
Block
end
/* synchronization */
| atomic do
Block
end
/* C integration */
| native [`/´(pure|const|nohold|plain)] `(´ LIST(ID_nat) `)´
| native `/´(pre|pos) do
<code definitions in C>
end
| native `/´ end
| `{´ {<code in C> | `@´ (`(´Exp`)´|Exp)} `}´ /* `@@´ escapes to `@´ */
// Nat_Call ::=
| [call] Exp
/* finalization */
| do [Stmt] Finalize
| var [`&´|`&?´] Type ID_int `=´ `&´ (Nat_Call | Code_Call) Finalize
// where
Finalize ::= finalize [ `(´ LIST(Loc) `)´ ] with
Block
[ pause with Block ]
[ resume with Block ]
end
/* Lua integration */
// Lua_State ::=
| lua `[´ [Exp] `]´ do
Block
end
// Lua_Stmts ::=
| `[´ {`=´} `[´
{ {<code in Lua> | `@´ (`(´Exp`)´|Exp)} } /* `@@´ escapes to `@´ */
`]´ {`=´} `]´
/* Abstractions */
/* Data */
| data ID_abs [as (nothing|Exp)] [ with
Dcls `;´ { Dcls `;´ }
end ]
/* Code */
// Code_Tight ::=
| code/tight Mods ID_abs `(´ Params `)´ `->´ Type
// Code_Await ::=
| code/await Mods ID_abs `(´ Params `)´
[ `->´ `(´ Params `)´ ]
`->´ (Type | NEVER)
[ throws LIST(ID_abs) ]
// where
Params ::= none | LIST(Dcls)
/* code implementation */
| (Code_Tight | Code_Await) do
Block
end
/* code invocation */
// Code_Call ::=
| call Mods Abs_Cons
// Code_Await ::=
| await Mods Abs_Cons
// Code_Spawn ::=
| spawn Mods Abs_Cons [in Loc]
| kill Loc [ `(` Exp `)` ]
// where
Mods ::= [`/´dynamic | `/´static] [`/´recursive]
Abs_Cons ::= [Loc `.´] ID_abs `(´ LIST(Data_Cons|Vec_Cons|Exp|`_´) `)´
/* Assignments */
| (Loc | `(´ LIST(Loc|`_´) `)´) `=´ Sources
// where
Sources ::= ( Do
| Emit_Ext
| Await
| Watching
| Thread
| Lua_Stmts
| Code_Await
| Code_Spawn
| Vec_Cons
| Data_Cons
| Exp
| `_´ )
Vec_Cons ::= (Loc | Exp) Vec_Concat { Vec_Concat }
| `[´ [LIST(Exp)] `]´ { Vec_Concat }
// where
Vec_Concat ::= `..´ (Exp | Lua_Stmts | `[´ [LIST(Exp)] `]´)
Data_Cons ::= (val|new) Abs_Cons
/* Identifiers */
ID ::= [a-zA-Z0-9_]+
ID_int ::= ID // ID beginning with lowercase
ID_ext ::= ID // ID all in uppercase, not beginning with digit
ID_abs ::= ID {`.´ ID} // IDs beginning with uppercase, containining at least one lowercase)
ID_field ::= ID // ID not beginning with digit
ID_nat ::= ID // ID beginning with underscore
ID_type ::= ( ID_nat | ID_abs
| none
| bool | on/off | yes/no
| byte
| r32 | r64 | real
| s8 | s16 | s32 | s64
| u8 | u16 | u32 | u64
| int | uint | integer
| ssize | usize )
/* Types */
Type ::= ID_type { `&&´ } [`?´]
/* Wall-clock values */
WCLOCKK ::= [NUM h] [NUM min] [NUM s] [NUM ms] [NUM us]
WCLOCKE ::= `(´ Exp `)´ (h|min|s|ms|us)
/* Literals */
NUM ::= [0-9] ([0-9]|[xX]|[A-F]|[a-f]|\.)* // regex
STR ::= " [^\"\n]* " // regex
/* Expressions */
Exp ::= NUM | STR | null | true | false | on | off | yes | no
| `(´ Exp `)´
| Exp <binop> Exp
| <unop> Exp
| Exp (`:´|`.´) (ID_int|ID_nat)
| Exp (`?´|`!´)
| Exp `[´ Exp `]´
| Exp `(´ [ LIST(Exp) ] `)´
| Exp is Type
| Exp as Type
| Exp as `/´(nohold|plain|pure)
| sizeof `(´ (Type|Exp) `)´
| Nat_Call | Code_Call
| ID_int
| ID_nat
| outer
/* Locations */
Loc ::= Loc [as (Type | `/´(nohold|plain|pure)) `)´
| [`*´|`$´] Loc
| Loc { `[´Exp`]´ | (`:´|`.´) (ID_int|ID_nat) | `!´ }
| ID_int
| ID_nat
| outer
| `{´ <code in C> `}´
| `(´ Loc `)´
/* Operator Precedence */
/* lowest priority */
// locations
* $
: . ! []
as
// expressions
is as // binops
or
and
!= == <= >= < >
|
^
&
<< >>
+ -
* / %
not + - ~ $$ $ * && & // unops
: . ! ? () []
/* highest priority */
/* Other */
// single-line comment
/** nested
/* multi-line */
comments **/
# preprocessor directive
TODO: statements that do not require ;