Syntax Guide

This guide provides a practical introduction to GLaDOS syntax with examples.

Program Structure

Every GLaDOS program consists of one or more functions. The main function is the entry point.

int main() {
    return 0;
}

Functions

Function Declaration

Functions are declared with a return type, name, parameters, and body:

<return_type> <name>(<parameters>) {
    <statements>
}

Example:

int add(int a, int b) {
    return a + b;
}

Function Parameters

Functions can take zero or more parameters:

int getFortyTwo() {
    return 42;
}

int multiply(int x, int y) {
    return x * y;
}

Return Statements

Every non-void function must return a value on all code paths:

int abs(int x) {
    if (x < 0) {
        return -x;
    } else {
        return x;
    }
}

int bad(int x) {
    if (x > 0) {
        return 1;
    }
}

Function Prototypes (Forward Declarations)

Functions can be declared before they are defined using prototypes. This enables mutual recursion and allows you to organize code with definitions after usage.

Syntax:

<return_type> <function_name>(<parameters>);

Examples:

int helper(int x);
bool isValid(int value);

int helper(int x) {
    return x * 2;
}

bool isValid(int value) {
    return helper(value) > 0;
}

Use Cases:

• Mutual recursion between functions
• Organize code with definitions after main
• Separate interface from implementation

Mutual Recursion Example:

int isEven(int n);
int isOdd(int n);

int isEven(int n) {
    if (n == 0) {
        return 1;
    }
    return isOdd(n - 1);
}

int isOdd(int n) {
    if (n == 0) {
        return 0;
    }
    return isEven(n - 1);
}

Important Notes:

• Prototype signature must match the actual function definition
• Parameters can be named in prototypes, but names are ignored
• Prototypes are particularly useful for mutually recursive functions

Variables

Declaration

Variables must be declared with a type:

int x;
bool flag;

Initialization

Variables can be initialized when declared:

int x = 10;
bool isReady = true;

Assignment

Variables can be assigned after declaration:

int x;
x = 5;
x = x + 1;

Types

GLaDOS supports four primitive types:

Type Safety

GLaDOS is strictly typed. You cannot mix types:

int x = true;

int y = 5 + true;

int x = 42;
bool flag = false;

Operators

Arithmetic Operators

int a = 10 + 5;
int b = 10 - 5;
int c = 10 * 5;
int d = 10 / 5;

Note: Division by zero is detected at compile-time for literals:

int x = 10 / 0;

Comparison Operators

All comparison operators return bool:

bool a = 5 == 5;
bool b = 5 != 3;
bool c = 5 < 10;
bool d = 5 > 10;
bool e = 5 <= 5;
bool f = 5 >= 10;

Logical Operators

bool a = true && false;
bool b = true || false;

Operator Precedence

From highest to lowest:

1. *, / (Multiplicative)
2. +, - (Additive)
3. <, >, <=, >=, ==, != (Comparison)
4. && (Logical AND)
5. || (Logical OR)

Use parentheses to override precedence:

int x = 2 + 3 * 4;
int y = (2 + 3) * 4;

Control Flow

If Statements

if (condition) {

}

If-Else Statements

if (condition) {

} else {

}

Example:

int max(int a, int b) {
    if (a > b) {
        return a;
    } else {
        return b;
    }
}

While Loops

while (condition) {

}

Example:

int factorial(int n) {
    int result = 1;
    while (n > 0) {
        result = result * n;
        n = n - 1;
    }
    return result;
}

Important: The condition must be a bool:

while (x) {
    x = x - 1;
}

while (x > 0) {
    x = x - 1;
}

For Loops

for (init; condition; increment) {

}

Example:

int sum(int n) {
    int total = 0;
    for (int i = 1; i <= n; i = i + 1) {
        total = total + i;
    }
    return total;
}

All clauses are optional:

for (;;) {
    if (done) {
        return;
    }
}

for (int i = 0; i < 10; i = i + 1) {

}

int i = 0;
for (; i < 10; i = i + 1) {

}

int i = 0;
for (; i < 10;) {
    i = i + 1;
}

Init clause can be declaration or assignment:

for (int i = 0; i < 10; i = i + 1) {

}

int i;
for (i = 0; i < 10; i = i + 1) {

}

Important: The condition must be a bool (when provided):

for (int i = 0; i < 10; i = i + 1) {

}

int i = 0;
for (; i;) {
    i = i - 1;
}

Comments

GLaDOS supports C-style comments:

// Single-line comment

/*
   Multi-line
   comment
*/

int x = 42;

Semicolons

Following in the footsteps of King Terry Davis and HolyC, semicolons are optional after statements in GLaDOS. We know this might make some of you anxious, but the program will run either way - even if they're mixed up in the same function!

int x = 5;
int y = 10;
return x + y;

int x = 5
int y = 10
return x + y

int x = 5;
int y = 10
return x + y;

if (x > 0) {
    return x
}

if (x > 0) {
    return x;
}

Use them, don't use them, mix them - GLaDOS doesn't judge. Code the way Terry intended: free.

Important Exception:

Semicolons are required in for loop syntax to separate the three clauses:

for (int i = 0; i < 10; i = i + 1) {

}

for (int i = 0; i < 10; i = i + 1) {

}

The semicolons between init, condition, and increment clauses in for loops are mandatory, even though semicolons after statements inside the loop body remain optional.

Function Calls

Functions are called by name with arguments:

int result = add(5, 3);
int answer = factorial(10);

Recursion

Functions can call themselves:

int fib(int n) {
    if (n <= 1) {
        return n;
    }
    return fib(n - 1) + fib(n - 2);
}

Expression Statements

Any expression can be used as a statement (useful for function calls with side effects):

int print(int x) {
    return x;
}

int main() {
    print(42);
    return 0;
}