ParaCL — Parasyl Language Interpreter

ParaCL is a simple interpreter for the Parasyl programming language, whose syntax resembles C.
The interpreter reads a program from standard input and outputs the results to standard output.

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📜 Parasyl Language Overview

• All variables are of type int.

• A program consists of a sequence of statements.

• Supported control structures:

  • if and else
  • while

• Assignment and arithmetic expressions.

• Postfix increment and decrement operators: x++, x--.

• Input from keyboard: x = ?;.

• Output to screen: print x;.

• Comments:

  • Single-line: // comment
  • Multi-line: /* comment */

• Operator precedence (from highest to lowest):

  1. Postfix increment/decrement: ++, --
  2. Unary minus: -
  3. Multiplication and division: *, /
  4. Addition and subtraction: +, -
  5. Comparisons: >, <, >=, <=, ==, !=

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Syntax of Main Constructs

if (expression) {
  // if body
} else
  // else body (optional)

while (expression) {
  // loop body
}

x = 1;
x = ?;    // input from keyboard
x++;
x--;
print x;

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Variable Scope

Variables are valid within the block delimited by { ... }. Accessing a variable outside its scope causes an error.

{
  y = 1;
}
print y;  // Error: variable y is not defined

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Error Handling

Using undeclared variables or accessing variables out of scope results in a detailed error message indicating the line and position.

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Example Program

To finish input in the terminal, press Ctrl + C

fst = 0;
snd = 1;
iters = ?;

while (iters-- > 0)
{
  tmp = fst;
  snd += tmp;
}

print snd;

y = 1;
x = ?;
while (((++x))++ > y)
{
  print /* comment */ (y == x);
  x -= 100;
}

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⚙️ Build and Run

mkdir build && cd build
cmake ..
cmake --build .
ctest