A simple calculator with rust using WASM

WebAssembly with rust

Rust is the most suitable language for WebAssembly. This is because of the small runtime, excellent efficiency, and a memory-safe language.

Today, we’re going to look into running a simple calculator rust program using wasmtime.

Installing rust in ubuntu

The first step is to setup rust in your local OS, I’m using ubuntu so here’s the command for that:

curl https://sh.rustup.rs -sSf | sh

Install Wasmtime

curl https://wasmtime.dev/install.sh -sSf | bash

Install the WebAssembly Rust toolchain:​

rustup target install wasm32-wasi

Rust Code​

We need to create a rust application with the command:

cargo new example
cd example/src

Create Application

For a simple calculator, add the following code to the main.rs file:

use std::io::{stdin, stdout, Write};
fn read(input: &mut String) {
    stdout().flush()
        .expect("failed to flush");
    stdin().read_line(input)
        .expect("failed to read");
}
fn main() {
    println!("welcome to engineer man's calculator!");
    println!("---------");
loop {
        let mut num1 = String::new();
        let mut num2 = String::new();
        let mut operator = String::new();
print!("what is the first number?: ");
        read(&mut num1);
print!("what is the second number?: ");
        read(&mut num2);
print!("what operation would you like to do? [+-*/]: ");
        read(&mut operator);
let num1: f32 = num1.trim().parse().unwrap();
        let num2: f32 = num2.trim().parse().unwrap();
        let operator: char = operator.trim().chars().next().unwrap();
let operators = String::from("+-*/");
if !operators.contains(operator) {
            println!("unknown operator");
            continue;
        }
let result = match operator {
            '+' => num1 + num2,
            '-' => num1 - num2,
            '*' => num1 * num2,
            '/' => num1 / num2,
            _ => panic!("error in operator")
        };
println!("the result of {} {} {} = {}", num1, operator, num2, result);
    }
}

Simple calculator code(edited in vim)

Compiling Rust Code​

1. Compile using cargo to verify the code:

cargo build
cargo run

12–29–30

2. Compile to wasm

rustc main.rs --target wasm32-wasi3.

Run the program:

wasmtime main.wasm

12–50–09

Yaaay! We finally executed our calculator in rust using WASM!