symbol

A textual denotation having special meaning to the compiler. The value can be determined from the text of the basic symbol.

Declaración

Sintaxis

symbol
    = Program(symbol_table symtab, identifier name, identifier* dependencies,
        stmt* body)
    | Module(symbol_table symtab, identifier name, identifier* dependencies,
        bool loaded_from_mod, bool intrinsic)
    | Function(symbol_table symtab, identifier name, expr* args, stmt* body,
        expr? return_var, abi abi, access access, deftype deftype,
        string? bindc_name, bool elemental, bool pure, bool module, bool inline,
        bool static, ttype* type_params, symbol* restrictions, bool is_restriction)
    | GenericProcedure(symbol_table parent_symtab, identifier name,
        symbol* procs, access access)
    | CustomOperator(symbol_table parent_symtab, identifier name,
        symbol* procs, access access)
    | ExternalSymbol(symbol_table parent_symtab, identifier name,
        symbol external, identifier module_name, identifier* scope_names,
        identifier original_name, access access)
    | StructType(symbol_table symtab, identifier name, identifier* members,
        abi abi, access access, symbol? parent)
    | EnumType(symbol_table symtab, identifier name, identifier* members,
        abi abi, access access, enumtype enum_value_type, ttype type, symbol? parent)
    | UnionType(symbol_table symtab, identifier name, identifier* members,
        abi abi, access access, symbol? parent)
    | Variable(symbol_table parent_symtab, identifier name, intent intent,
        expr? symbolic_value, expr? value, storage_type storage, ttype type,
        abi abi, access access, presence presence, bool value_attr)
    | ClassType(symbol_table symtab, identifier name, abi abi, access access)
    | ClassProcedure(symbol_table parent_symtab, identifier name,
    identifier?
        self_argument, identifier proc_name, symbol proc, abi abi)
    | AssociateBlock(symbol_table symtab, identifier name, stmt* body)
    | Block(symbol_table symtab, identifier name, stmt* body)

Argumentos

Argument Name

Denotes

symtab

local symbol table

name

symbol name for easy lookup

dependencies

dependencies of symbol

body

statement body

loaded_from_mod

boolean value if loaded from mode

intrinsic

boolean value if intrinsic

args

arguments of expression

abi

source

original_name

original symbol

parent_symtab

where symbol is stored

scope_names

list of names if the symbol is in a nested symbol table

storage_type

Default/Save/Parameter/Allocatable

access

Public/Private

intent

Local/In/Out/InOut/ReturnVar/Unspecified

deftype

Implementation/Interface

presence

Required/Optional

self_argument

the argument which contains the object calling the class procedure

Valores devueltos

None.

Descripción

Each symbol has either symtab (local symbol table) or parent_symtab (where this symbol is stored). One can get to parent_symtab via symtab, so only one is present.

Each symbol has a name for easy lookup of the name of the symbol when only having a pointer to it.

abi=Source means the symbol’s implementation is included (full ASR), otherwise it is external (interface ASR, such as procedure interface).

SubroutineCall/FunctionCall store the actual final resolved subroutine or function (name member). They also store the original symbol (original_name), which can be one of: null, GenericProcedure or ExternalSymbol.

When a module is compiled, it is parsed into full ASR, an object file is produced, the full ASR (abi=Source, «body» is non-empty) is transformed into interface ASR (abi=LFortran, «body» is empty). Both interface and full ASR is saved into the mod file.

When a module is used, it is first looked up in the symbol table (as either full or interface ASR) and used if it is present. Otherwise a mod file is found on the disk, loaded (as either full or interface ASR for LFortran’s mod file, depending on LFortran’s compiler options; or for GFortran’s mod file the corresponding interface ASR is constructed with abi=GFortran) and used. After the ASR is loaded, the symbols that are used are represented as ExternalSymbols in the current scope of the symbol table.

ExternalSymbol represents symbols that cannot be looked up in the current scoped symbol table. As an example, if a variable is defined in a module, but used in a nested subroutine, that is not an external symbol because it can be resolved in the current symbol table (nested subroutine) by following the parents. However if a symbol is used from a different module, then it is an external symbol, because usual symbol resolution by going to the parents will not find the definition. The module_name member is the name of the module the symbol is in, the scope_names is a list of names if the symbol is in a nested symbol table. For example if it is a local variable in a function f that is nested in function g, then scope_names=[g, f].

REPL: each cell is parsed into full ASR, compiled + executed, the full ASR is transformed into interface ASR (abi=LFortran) and kept in the symbol table. A new cell starts with an empty symbol table, whose parent symbol table is the previous cell. That allows function / declaration shadowing.

Symbols in LFortran are:

  1. Program

  2. Module

  3. Function

  4. GenericProcedure

  5. CustomOperator

  6. ExternalSymbol

  7. DerivedType

  8. Variable

  9. ClassType

  10. ClassProcedure

  11. AssociateBlock

  12. Block

Tipos

Special meaning textual denotations.

Ejemplos

Example of function:

integer function a()
end

ASR:

(TranslationUnit
    (SymbolTable
        1
        {
            a:
                (Function
                    (SymbolTable
                        2
                        {
                            a:
                                (Variable
                                    2
                                    a
                                    ReturnVar
                                    ()
                                    ()
                                    Default
                                    (Integer 4 [])
                                    Source
                                    Public
                                    Required
                                    .false.
                                )

                        })
                    a
                    []
                    []
                    (Var 2 a)
                    Source
                    Public
                    Implementation
                    ()
                    .false.
                    .false.
                    .false.
                    .false.
                    .false.
                    []
                    []
                    .false.
                )

        })
    []
)

Example of GenericProcedure:

module stdlib_quadrature_simps
    interface simps38_weights
        module procedure simps38_weights_dp
    end interface simps38_weights

contains

    function simps38_weights_dp(x) result(w)
        real(8), intent(in) :: x(4)
        real(8) :: w(size(x))
    end function simps38_weights_dp

    subroutine simps38_weights_dp_use(x1)
        real(8), intent(in) :: x1(4)
        print *, simps38_weights(x1)
    end subroutine simps38_weights_dp_use
end module

program stdlib_quadrature
use stdlib_quadrature_simps, only: simps38_weights_dp
implicit none
real(8) :: x1(4)
print *, simps38_weights_dp(x1)
end program

ASR:

(TranslationUnit
    (SymbolTable
        1
        {
            stdlib_quadrature:
                (Program
                    (SymbolTable
                        5
                        {
                            simps38_weights_dp:
                                (ExternalSymbol
                                    5
                                    simps38_weights_dp
                                    2 simps38_weights_dp
                                    stdlib_quadrature_simps
                                    []
                                    simps38_weights_dp
                                    Public
                                ),
                            x1:
                                (Variable
                                    5
                                    x1
                                    Local
                                    ()
                                    ()
                                    Default
                                    (Real 8 [((IntegerConstant 1 (Integer 4 []))
                                    (IntegerConstant 4 (Integer 4 [])))])
                                    Source
                                    Public
                                    Required
                                    .false.
                                )

                        })
                    stdlib_quadrature
                    [stdlib_quadrature_simps]
                    [(Print
                        ()
                        [(FunctionCall
                            5 simps38_weights_dp
                            ()
                            [((Var 5 x1))]
                            (Real 8 [((IntegerConstant 1 (Integer 4 []))
                            (IntegerConstant 4 (Integer 4 [])))])
                            ()
                            ()
                        )]
                        ()
                        ()
                    )]
                ),
            stdlib_quadrature_simps:
                (Module
                    (SymbolTable
                        2
                        {
                            simps38_weights:
                                (GenericProcedure
                                    2
                                    simps38_weights
                                    [2 simps38_weights_dp]
                                    Public
                                ),
                            simps38_weights_dp:
                                (Function
                                    (SymbolTable
                                        3
                                        {
                                            w:
                                                (Variable
                                                    3
                                                    w
                                                    ReturnVar
                                                    ()
                                                    ()
                                                    Default
                                                    (Real 8 [((IntegerConstant 1 (Integer 4 []))
                                                    (IntegerConstant 4 (Integer 4 [])))])
                                                    Source
                                                    Public
                                                    Required
                                                    .false.
                                                ),
                                            x:
                                                (Variable
                                                    3
                                                    x
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Real 8 [((IntegerConstant 1 (Integer 4 []))
                                                    (IntegerConstant 4 (Integer 4 [])))])
                                                    Source
                                                    Public
                                                    Required
                                                    .false.
                                                )

                                        })
                                    simps38_weights_dp
                                    [(Var 3 x)]
                                    []
                                    (Var 3 w)
                                    Source
                                    Public
                                    Implementation
                                    ()
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    []
                                    []
                                    .false.
                                ),
                            simps38_weights_dp_use:
                                (Function
                                    (SymbolTable
                                        4
                                        {
                                            x1:
                                                (Variable
                                                    4
                                                    x1
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Real 8 [((IntegerConstant 1 (Integer 4 []))
                                                    (IntegerConstant 4 (Integer 4 [])))])
                                                    Source
                                                    Public
                                                    Required
                                                    .false.
                                                )

                                        })
                                    simps38_weights_dp_use
                                    [(Var 4 x1)]
                                    [(Print
                                        ()
                                        [(FunctionCall
                                            2 simps38_weights_dp
                                            2 simps38_weights
                                            [((Var 4 x1))]
                                            (Real 8 [((IntegerConstant 1 (Integer 4 []))
                                            (IntegerConstant 4 (Integer 4 [])))])
                                            ()
                                            ()
                                        )]
                                        ()
                                        ()
                                    )]
                                    ()
                                    Source
                                    Public
                                    Implementation
                                    ()
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    []
                                    []
                                    .false.
                                )

                        })
                    stdlib_quadrature_simps
                    []
                    .false.
                    .false.
                )

        })
    []
)

Example of Module and CustomOperator:

module stdlib_string_type
    type :: string_type
        sequence
        private
        character(len=:), allocatable :: raw
    end type string_type

    interface write(formatted)
        module procedure :: write_formatted
    end interface

    interface read(formatted)
        module procedure :: read_formatted
    end interface

contains

subroutine write_formatted(string, unit, iotype, v_list, iostat, iomsg)
    type(string_type), intent(in) :: string
    integer, intent(in) :: unit
    character(len=*), intent(in) :: iotype
    integer, intent(in) :: v_list(:)
    integer, intent(out) :: iostat
    character(len=*), intent(inout) :: iomsg
end subroutine write_formatted

subroutine read_formatted(string, unit, iotype, v_list, iostat, iomsg)
    type(string_type), intent(inout) :: string
    integer, intent(in) :: unit
    character(len=*), intent(in) :: iotype
    integer, intent(in) :: v_list(:)
    integer, intent(out) :: iostat
    character(len=*), intent(inout) :: iomsg
    character(len=:), allocatable :: line
end subroutine read_formatted

end module

program string_14
end program

ASR:

(TranslationUnit
    (SymbolTable
        1
        {
            stdlib_string_type:
                (Module
                    (SymbolTable
                        2
                        {
                            formatted:
                                (CustomOperator
                                    2
                                    formatted
                                    [2 read_formatted]
                                    Public
                                ),
                            read_formatted:
                                (Function
                                    (SymbolTable
                                        5
                                        {
                                            iomsg:
                                                (Variable
                                                    5
                                                    iomsg
                                                    InOut
                                                    ()
                                                    ()
                                                    Default
                                                    (Character 1 -1 () [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            iostat:
                                                (Variable
                                                    5
                                                    iostat
                                                    Out
                                                    ()
                                                    ()
                                                    Default
                                                    (Integer 4 [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            iotype:
                                                (Variable
                                                    5
                                                    iotype
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Character 1 -1 () [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            line:
                                                (Variable
                                                    5
                                                    line
                                                    Local
                                                    ()
                                                    ()
                                                    Allocatable
                                                    (Character 1 -2 () [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            string:
                                                (Variable
                                                    5
                                                    string
                                                    InOut
                                                    ()
                                                    ()
                                                    Default
                                                    (Struct
                                                        2 string_type
                                                        []
                                                    )
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            unit:
                                                (Variable
                                                    5
                                                    unit
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Integer 4 [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            v_list:
                                                (Variable
                                                    5
                                                    v_list
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Integer 4 [(()
                                                    ())])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                )

                                        })
                                    read_formatted
                                    [(Var 5 string)
                                    (Var 5 unit)
                                    (Var 5 iotype)
                                    (Var 5 v_list)
                                    (Var 5 iostat)
                                    (Var 5 iomsg)]
                                    [(ImplicitDeallocate
                                        [5 line]
                                    )]
                                    ()
                                    Source
                                    Private
                                    Implementation
                                    ()
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    []
                                    []
                                    .false.
                                ),
                            string_type:
                                (StructType
                                    (SymbolTable
                                        3
                                        {
                                            raw:
                                                (Variable
                                                    3
                                                    raw
                                                    Local
                                                    ()
                                                    ()
                                                    Allocatable
                                                    (Character 1 -2 () [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                )

                                        })
                                    string_type
                                    [raw]
                                    Source
                                    Private
                                    ()
                                ),
                            write_formatted:
                                (Function
                                    (SymbolTable
                                        4
                                        {
                                            iomsg:
                                                (Variable
                                                    4
                                                    iomsg
                                                    InOut
                                                    ()
                                                    ()
                                                    Default
                                                    (Character 1 -1 () [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            iostat:
                                                (Variable
                                                    4
                                                    iostat
                                                    Out
                                                    ()
                                                    ()
                                                    Default
                                                    (Integer 4 [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            iotype:
                                                (Variable
                                                    4
                                                    iotype
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Character 1 -1 () [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            string:
                                                (Variable
                                                    4
                                                    string
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Struct
                                                        2 string_type
                                                        []
                                                    )
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            unit:
                                                (Variable
                                                    4
                                                    unit
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Integer 4 [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            v_list:
                                                (Variable
                                                    4
                                                    v_list
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Integer 4 [(()
                                                    ())])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                )

                                        })
                                    write_formatted
                                    [(Var 4 string)
                                    (Var 4 unit)
                                    (Var 4 iotype)
                                    (Var 4 v_list)
                                    (Var 4 iostat)
                                    (Var 4 iomsg)]
                                    []
                                    ()
                                    Source
                                    Private
                                    Implementation
                                    ()
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    []
                                    []
                                    .false.
                                )

                        })
                    stdlib_string_type
                    []
                    .false.
                    .false.
                ),
            string_14:
                (Program
                    (SymbolTable
                        6
                        {

                        })
                    string_14
                    []
                    []
                )

        })
    []
)

Example of ClassProcedure:

module bitset
    type, abstract :: bitset_type

        private
        integer(8) :: num_bits

    contains

        procedure(all_abstract), deferred, pass(self) :: all

    end type bitset_type


    abstract interface

        elemental function all_abstract( self ) result(all)
            import :: bitset_type
            logical :: all
            class(bitset_type), intent(in) :: self
        end function all_abstract
    end interface

end module

program debug
    implicit none
end program

ASR:

(TranslationUnit
    (SymbolTable
        1
        {
            bitset:
                (Module
                    (SymbolTable
                        2
                        {
                            all_abstract:
                                (Function
                                    (SymbolTable
                                        4
                                        {
                                            all:
                                                (Variable
                                                    4
                                                    all
                                                    ReturnVar
                                                    ()
                                                    ()
                                                    Default
                                                    (Logical 4 [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                ),
                                            self:
                                                (Variable
                                                    4
                                                    self
                                                    In
                                                    ()
                                                    ()
                                                    Default
                                                    (Class
                                                        2 bitset_type
                                                        []
                                                    )
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                )

                                        })
                                    all_abstract
                                    [(Var 4 self)]
                                    []
                                    (Var 4 all)
                                    Source
                                    Private
                                    Interface
                                    ()
                                    .true.
                                    .false.
                                    .false.
                                    .false.
                                    .false.
                                    []
                                    []
                                    .false.
                                ),
                            bitset_type:
                                (StructType
                                    (SymbolTable
                                        3
                                        {
                                            all:
                                                (ClassProcedure
                                                    3
                                                    all
                                                    all_abstract
                                                    2 all_abstract
                                                    Source
                                                ),
                                            num_bits:
                                                (Variable
                                                    3
                                                    num_bits
                                                    Local
                                                    ()
                                                    ()
                                                    Default
                                                    (Integer 8 [])
                                                    Source
                                                    Private
                                                    Required
                                                    .false.
                                                )

                                        })
                                    bitset_type
                                    [num_bits]
                                    Source
                                    Private
                                    ()
                                )

                        })
                    bitset
                    []
                    .false.
                    .false.
                ),
            debug:
                (Program
                    (SymbolTable
                        5
                        {

                        })
                    debug
                    []
                    []
                )

        })
    []
)

Ver también