Constants and Constant Expressions (const)

Cm uses the const keyword to define compile-time constants. Since v0.12.0, you can use constant variables and expressions for array sizes.

Basic Usage

Defining const Variables

const int MAX_SIZE = 100;
const double PI = 3.14159;
const bool DEBUG = true;

int main() {
    println("MAX_SIZE = {MAX_SIZE}");  // MAX_SIZE = 100
    println("PI = {PI}");              // PI = 3.14159
    return 0;
}

Using const for Array Sizes

const int SIZE = 10;
const int DOUBLE_SIZE = SIZE * 2;  // Constant expressions are evaluated

int main() {
    int[SIZE] arr1;           // int[10]
    int[DOUBLE_SIZE] arr2;    // int[20]
    
    println("arr1.size() = {arr1.size()}");  // 10
    println("arr2.size() = {arr2.size()}");  // 20
    
    return 0;
}

Constant Expressions

Expressions evaluated at compile time are called constant expressions.

Supported Operations

Examples

const int A = 10;
const int B = 20;

// Arithmetic
const int SUM = A + B;        // 30
const int PRODUCT = A * B;    // 200

// Bitwise
const int SHIFTED = A << 2;   // 40

// Ternary
const int MAX = A > B ? A : B;  // 20

// Use in array size
int[SUM] data;  // int[30]

Limitations

Current implementation has the following limitations:

• Only global scope const variables are supported
• Function calls cannot be included in constant expressions
• constexpr functions planned for future versions

Related Topics

• Variables - Variable basics
• Arrays - Array usage

Last Updated: 2026-02-08