Language Specification & Syntax

Detailed language reference covering types, explicit mutability, functions, pipeline operator, and structs.

NextViper Language Specification

Comprehensive reference for the NextViper syntax, lexical structure, type system, and control flow.

1. Variables & Mutability

NextViper enforces explicit mutability to eliminate state-related concurrency bugs.

Immutable Variables (`let`)

Variables declared with let cannot be mutated or rebound:

nextviper

let pi = 3.14159
let name = "NextViper"
// pi = 3.14  <-- Error: cannot reassign to immutable variable

Mutable Variables (`let mut`)

Variables intended to change must explicitly declare mut:

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let mut counter = 0
counter += 1
counter = counter * 2
print("Counter:", counter) // 2

2. Data Types

NextViper provides rich primitive and compound types:

Integers: Int (42, 1_000_000, 0xFF, 0b1010)

Floats: Float (3.14, 1e-4)

Booleans: Bool (true, false)

Strings: String (`"UTF-8 string with

escapes"`)

Arrays: [1, 2, 3, 4]

Objects / Dicts: {"key": "value", "status": 200}

Nil: nil (represents absence of value)

3. Functions & Closures

Standard Function

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fn calculate_loss(pred: Float, target: Float) -> Float {
    let diff = pred - target
    return diff * diff
}

Arrow Expression Function

For single-expression functions:

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fn square(x) => x * x
fn is_even(n) => n % 2 == 0

First-Class Functions & Lambdas

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let multiply = fn(a, b) => a * b
print(multiply(4, 5)) // 20

4. Pipeline Operator (`|>`)

NextViper includes a native pipeline operator to transform data fluently without nested parenthesis:

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let raw_data = "  12, 45, 78, 90  "

let clean_total = raw_data
    |> trim()
    |> split(",")
    |> map(fn(s) => to_int(trim(s)))
    |> filter(fn(n) => n > 20)
    |> sum()

print("Total:", clean_total)

5. Control Flow

If / Else

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if score >= 90 {
    print("Grade: A")
} else if score >= 80 {
    print("Grade: B")
} else {
    print("Grade: C")
}

Loops

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// For in range
for i in 0..5 {
    print("Index:", i)
}

// For in collection
let items = ["data", "tensor", "ai"]
for item in items {
    print("Module:", item)
}

// While loop
let mut n = 10
while n > 0 {
    n -= 1
}