// Área: Compiladores
// Professor: Cássio Pinheiro
// Tema: Implementação de Interpretador de Derivação.
// Ultima Atualização: 10/10/2025

#include <iostream>
#include <string>

#define tam_linha 19
#define isTokenTp( token ) ( sTokenTp[ nIdx ] == token ? true: false )
#define isTokenNm( token ) ( sTokenNm[ nIdx ] == token ? true: false )

using namespace std;

bool stmt( void );
bool stmtlist( void );
void showTerm( void );
bool expr( bool bFlag );
bool ehTipo( string cTipo );
bool optr( void );
bool id( void );
bool num( void );

string sTokenNm[ tam_linha ] = {  "if", "(", "x", ">", "9", ")", "{", "x", "=",
                                  "0", ";", "y", "=", "y", "+", "1", ";", "}", "@" };
string sTokenTp[ tam_linha ] = {  "st", "sm", "id", "op", "nr", "sm", "sm", "id", "op",
                                  "nr", "sm", "id", "op", "id", "op", "nr", "sm", "sm", "@" };
int nIdx = 0;

int main() {
    stmt();
    return 0;
}

bool stmt( void ) {
    if( isTokenNm( "@" ) ) return( false );
    if( id() ) {
        if( isTokenNm( "=" ) ) {
            showTerm();
            if( expr( true ) ) {
                if( isTokenNm( ";" ) ) {
                    showTerm();
                    if( isTokenNm( "}" ) ) showTerm();
                    if( stmt() ) return( true );
                    return( false );
                }
            }
            else return( false );
        }
        return( false );
    }
    else {
        if( isTokenNm( "{" ) ) {
            showTerm();
            if( stmtlist() ) {
                if( isTokenNm( "}" ) ) {
                    showTerm();
                    return( true );
                }
                return( false );
            }
            return( false );
        }
        else {
            if( isTokenNm( "if" ) ) {
                showTerm();
                if( isTokenNm( "(" ) ) {
                    showTerm();
                    if( expr( true ) ) {
                       if( isTokenNm( ")" ) ) {
                          showTerm();
                          if( stmt() ) return( true );
                          return( false );
                       }
                       return( false );
                    }
                    return( false );
                }
                return( false );
            }
            return( false );
        }
    }
}

void showTerm( void ) {
    cout << sTokenNm[ nIdx++ ];
}

bool ehTipo( string cTipo ) {
    if( isTokenTp( cTipo ) ) {
        showTerm();
        return( true );
    }
    return( false );
}

bool optr( void ) {
    return( ehTipo( "op" ) );
}

bool id( void ) {
    return( ehTipo( "id" ) );
}

bool num( void ) {
    return( ehTipo( "nr" ) );
}

bool expr( bool bFlag ) {
    if( isTokenNm( "@" ) ) return( false );
    if( bFlag ) {
        nIdx++;
        if( isTokenTp( "op" ) ) {
            nIdx--;
            if( expr( false ) ) {
                if( optr() ) {
                   if( expr( true ) ) return( true );
                   return( false );
                }
                return( false );
            }
            return( false );
        }
        else {
          nIdx--;
          if( expr( false ) ) return( true );
          return( false );
        }
    }
    else {
        if( id() ) return( true );
        if( num() ) return( true );
        return( false );
    }
}

bool stmtlist( void ) {
    if( isTokenNm( "@" ) ) return( false );
    if( stmt() ) return( true );
    return( false );
}
by

C++ Online Compiler

Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C++ and start coding!

Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}