0xack13 / katascript

A simple scripting language

KataScript

A simple, header-only, scripting language with familiar syntax.

Index

• Tutorial
  • Variables
  • Functions
  • Loops
  • if/else
• Examples
  • Hello World
  • Fizzbuzz
  • Fibonacci Series
• C++ Integration
  • Invoke C++ From KataScript
  • Invoke KataScript From C++

Tutorial

Comments

Comments are anything in a line after // and will be ignored.

// this is a comment

Comments need not start at the beginnning of a line.

Variables

Simply attempt to use a variable and it will be created.

i = 5;

The variable i now stores the integer 5.

If you want to store a float or a string in i, you can do that too.

i = 5.0; // i is a float
i = "string value"; // i is now a string

KataScript is weakly typed, so values will upconvert for operations when necessary and you can assign anything to anything.

Functions

Functions are called with the syntax name(arg(s)...). For example:

print(100);
add("hello ", "world");

Functions are created using the func keyword. Functions may return values, but it is not strictly required.

func add1(a) {
  return a + 1;
}

Loops

while() and for() are synonyms that mean start a loop. Either way you can put 1-3 expressions seperated by semicolons inside the parens.

• 1 expression: behaves like a standard while loop
• 2 expressions: behaves like a for loop with no initialization statment
• 3 expressions: behaves like a standard for loop

Then just put the loop contents inside of curly brackets:

for (i = 0; i < 100; i++) {
  print(i);
}

if/else

if/else if/else all work how you'd expect.

if (5 == 5) { 
  print("pie"); 
} else if (5 == 6) { 
  print("cake"); 
} else { 
  print("coffee"); 
}

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Examples

Hello World

print("hello world");

Fizzbuzz

func fizzbuzz(n) {
  for(i=1;i<=n;i++) { 
    if (i % 15 == 0) { 
      print("fizzbuzz"); 
    } else if (i % 3 == 0) { 
      print("fizz"); 
    } else if (i % 5 == 0) { 
      print("buzz"); 
    } else { 
      print(i);
    } 
  }
}

The Fibonacci Series

func fib(c) {
  i = 0;
  j = 1;
  while(i<c) { 
    print(i); 
    i += j; 
    a = i;
    i = j;
    j = a;
  }
}

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C++ Integration

KataScript is a single header file. To include KataScript into your project simply put KataScript.hpp into your project and #include it.

Invoke C++ From KataScript

If we want to call C++ code from inside the script, we can register the code as a function any time after calling the KataScriptInterpreter constructor; (note that the function will be placed in the current scope)

Here's a function to wrap for the example: (in C++)

int integrationExample(int a) {
  return a * a;
}

Then here's how we register it for use inside of KataScript: (note, this will overwrite any existing function with the same name, so you can use that to redirect the print function for example)

KataScript::KataScriptInterpreter interp;
interp.newFunction("integrationExample", [](KataScript::KSFunctionArgs args) {
  // Dereference argument
  auto val = *args[0];
  // Coerce type
  val.hardconvert(KataScript::KSType::INT);
  // Call c++ code
  auto result = integrationExample(val.getInt());
  // Wrap and return
  return std::make_shared<KataScript::KSValue>(result);
});

Now we can call that function from inside our scripts.

Invoke KataScript From C++

We can also send commands from C++ into KataScript using the readLine function.

interp.readLine("i = integrationExample(4);");

Now i contains 16 and is an int. If we want to pull that value out, we can do that too!

auto varRef = interp.resolveVariable("i");

// visit style
std::visit([](auto&& arg) {std::cout << arg; }, varRef->value);

// if the type is known
int i = varRef->getInt();

// switch style
switch (varRef->type) {
case KataScript::KSType::INT:
  std::cout << varRef->getInt();
  break;
case KataScript::KSType::FLOAT:
  std::cout << varRef->getFloat();
  break;
case KataScript::KSType::STRING:
  std::cout << varRef->getString();
  break;
}

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