symbol¶
A textual denotation having special meaning to the compiler. The value can be determined from the text of the basic symbol.
Declaration¶
Syntax¶
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)
| Union(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)
| Requirement(symbol_table symtab, identifier name, identifier* args, require_instantiation* requires)
| Template(symbol_table symtab, identifier name, identifier* args, require_instantiation* requires)
Arguments¶
Argument Name |
Denotes |
|---|---|
|
local symbol table |
|
symbol name for easy lookup |
|
dependencies of symbol |
|
statement body |
|
boolean value if loaded from mode |
|
boolean value if intrinsic |
|
arguments of expression |
|
source |
|
original symbol |
|
where symbol is stored |
|
list of names if the symbol is in a nested symbol table |
|
Default/Save/Parameter/Allocatable |
|
Public/Private |
|
Local/In/Out/InOut/ReturnVar/Unspecified |
|
Implementation/Interface |
|
Required/Optional |
|
the argument which contains the object calling the class procedure |
|
assigning types to requirement or template arguments |
Return values¶
None.
Description¶
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:
Program
Module
Function
GenericProcedure
CustomOperator
ExternalSymbol
DerivedType
Variable
ClassType
ClassProcedure
AssociateBlock
Block
Requirement
Template
Types¶
Special meaning textual denotations.
Examples¶
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
[]
[]
)
})
[]
)