recursive structs

[harsh loom]

hey, so I wanted to create something similar to this

struct a{
  struct b* ptr;
  int a, b, c;
}

struct b
{
  struct a a_val;
}

but it gives me an error type "b" does not name a type could anyone help?

[tacit gyro]

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[slender mason]

you need to forward declare it

[harsh loom]

do you mean to move struct b before struct a?

[slender mason]

no, thats not a forward declaration

[livid forum]

;compile

struct a{
  struct b* ptr;
  int a, b, c;
};

struct b
{
  struct a a_val;
};

[sullen zinc]

Compilation successful

holyblackcat | 82ms | c++ | x86-64 gcc 15.1 | godbolt.org

[livid forum]

This already compiles

If I add the ;s

[harsh loom]

wait a minute

[slender mason]

struct Foo; // declaration
// use Foo* or Foo&
struct Foo { // provide definition somewhere

};
``` is the typical route

[livid forum]

This already compiles
But this is written in C style. In C++ you'd typically write it as

struct a{
  b* ptr;
  int a, b, c;
};

struct b
{
  a a_val;
};

And this indeed doesn't compile until you add struct b; at the beginning before the first struct

[harsh loom]

oh it was in c++

[livid forum]

The C style works in C++ as well

[harsh loom]

I will show you my code

[livid forum]

The C style works in C++ as well
It just looks ugly

[harsh loom]

yeah, my actual code is in c++ but kind of like c

I haven't done that in my original code

I will sent it to you right now

[harsh loom]

struct ElifConditionals
{
  Value* exp;
  Program block;
  // ElifConditionals(**& v_exp, Program*& v_block)Value*:exp(v_exp), block(v_block){
  //   Node = NodeType::ElifConditionals_;
  // }
};

struct ElseConditionals
{
  Program block;
  // ElseConditionals(Program*& v_block):block(v_block){Node = NodeType::ElseConditionals_; }
  
};



struct Value
{ // types of expression
  // statements
  NodeType Node;
  union
  {
    E_O_F eof;
    Program program;
    //VarDec varDec;
    //VarConstDec varConstDec;
    //Conditionals conditionals;
    //ElifConditionals 
    //ElseConditionals,

    // both literals(value) and expressions
    BoolLiteral boolLiteral;
    IntLiteral intLiteral;
    NullVal nullval;

    // expressions
    AssignExpr assignExpr;
    Identifier identifier;
    BinaryArithExpr binaryArithExpr;
    BinaryBoolExpr binaryBoolExpr;
    BinaryBoolNumExpr binaryBoolNumExpr;
  };
  
};

it gives me error

src/Headers/../FrontEnd/Headers/AST.h:124:3: error: ‘Value’ does not name a type
  124 |   Value* exp;
      |   ^~~~~```

[livid forum]

Read the end of this message

[harsh loom]

so what is wrong with my code

it is compiled in c++

[livid forum]

Read the last sentence of the message I linked

[harsh loom]

oh

thanks

!solved