Tiny C++ Interpreter

Cpi is a tiny interpreter for C++20 or C++23.

Requirements

The following softwares are needed to build and execute cpi.
The compiler is used as interpreter of cpi internally.

• Qt tookit version 6
• Compiler - GNU C++ compiler, LLVM C++ compiler or MSVC C++ compiler

Install

Linux:

$ qmake
$ make
$ sudo make install
$ cpi -v
cpi 2.2.0

Windows (Command prompt for VS2022):

**********************************************************************
** Visual Studio 2022 Developer Command Prompt v17.14.7
** Copyright (c) 2025 Microsoft Corporation
**********************************************************************
[vcvarsall.bat] Environment initialized for: 'x64'
> C:\Qt\6.7.0\msvc2019_64\bin\qtenv2.bat
Setting up environment for Qt usage...
> cd (cpi root directory)
> qmake
> nmake
> cpi.bat -h        (Run cpi command)
Usage: cpi.exe [options] [file] [-]
Tiny C++ Interpreter.
Runs in interactive mode by default.
Options:
  -?, -h, --help  Displays help on commandline options.
  --help-all      Displays help, including generic Qt options.
  -v, --version   Displays version information.
Arguments:
  file            File to compile.
  -               Reads from stdin.

Interactive Mode

  $ cpi           (Run cpi.bat in windows)
  cpi 2.2.0
  Type ".help" for more information.
  Loaded INI file: /home/foo/.config/cpi/cpi.conf
  cpi> 3 << 23;        (Bitwise operation)
  25165824
  cpi> int a = 3;
  cpi> ~a;              (Complement)
  -4
  cpi> a ^ 2;           (XOR)
  1
  cpi> auto func = [](int n) { return n*n; };     (Lambda function)
  cpi> func(3);
  9
  cpi> .quit         ( or press ctrl+c )

Code can be pasted.

  $ cpi              (Run cpi.bat in windows)
  cpi> #include <map>         (Paste code here)
  #include <iostream>
  int main()
  {
    std::map<int, std::string> m = { {1, "one"}, {2, "two"} };
    if (auto it = m.find(2); it != m.end()) {
      std::cout << it->second << std::endl;
    }
  }              (Press enter)
  two            (The result of the executed output)

Executive mode

Save C++ source code as hello.cpp.

#include <iostream>
int main()
{
    std::cout << "Hello world\n";
    return 0;
}

Run cpi in command line.

  $ cpi hello.cpp
  Hello world

Immediately compiled and executed! Almost a script language, but the source file is also C++ program which a compiler can compile successfully.

Next code outputs a square root of input argument.
Specify options for compiler or linker with “CompileOptions: “ word. In this example, linking math library specified by “-lm” option.

#include <iostream>
#include <cmath>
#include <cstdlib>
int main(int argc, char *argv[])
{
    if (argc != 2) return 0;
    std::cout << sqrt(atoi(argv[1])) << std::endl;
    return 0;
}
// CompileOptions: -lm

  $ cpi sqrt.cpp 2
  1.41421
  $ cpi sqrt.cpp 3
  1.7320

The following is sample code for generator using coroutine.

#include <generator>
#include <iostream>
std::generator<int> num_generator(int from, int to)
{
    for (int i = from; i <= to; i++) {
        co_yield i;
    }
}
int main()
{
    long long sum = 0;
    for (auto v : num_generator(1, 1000000)) {
        sum += v;
    }
    std::cout << sum << std::endl;
    return 0;
}
// CompileOptions: -std=c++23

  $ cpi main.cpp
  500000500000

Furthermore, pkg-config command can be used for CompileOptions.

#include <cblas.h>
#include <iostream>
int main()
{
    // 2x2 Matrix
    int M = 2, N = 2, K = 2;
    double A[4] = {1.0, 2.0, 3.0, 4.0};
    double B[4] = {5.0, 6.0, 7.0, 8.0};
    double C[4];
    // General Matrix-Matrix multiplication
    cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans,
        M, N, K,
        1.0, A, K, B, N,
        0.0, C, N);
    // Print results
    std::cout << "Result of A * B = C:" << std::endl;
    for (int i = 0; i < 2; ++i) {
        for (int j = 0; j < 2; ++j) {
            std::cout << C[i * 2 + j] << " ";
        }
        std::cout << std::endl;
    }
    return 0;
}
// CompileOptions: `pkg-config --cflags --libs openblas`

 $ cpi dgemm.cpp
 Result of A * B = C:
 19 22
 43 50

Qt application can also be run.

#include <QApplication>
#include <QLabel>
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QLabel label("Hello, world!");
    label.setAlignment(Qt::AlignCenter);
    label.setWindowTitle("Hello");
    label.resize(200, 100);
    label.show();
    return app.exec();
}
// CompileOptions: `pkg-config --cflags --libs Qt6Widgets`

 $ cpi helloworld_qt.cpp

Running like a scripting language

Adding a shebang, save as hello.cpps. No longer compiled in a C++ compiler successfully.

#!/usr/bin/env cpi
#include <iostream>
int main()
{
    std::cout << "Hello world\n";
    return 0;
}

  $ chmod +x hello.cpps
  $ ./hello.cpps
  Hello world

Yes, a shell script. I named it CppScript.

Help

  cpi> .help
   .conf        Display the current values for various settings.
   .help        Display this help.
   .rm LINENO   Remove the code of the specified line number.
   .show        Show the current source code.
   .quit        Exit this program.

Download

Download Page

Web Site

http://treefrogframework.github.io/cpi/