61 lines
1.3 KiB
Rust
61 lines
1.3 KiB
Rust
const THREE_DAYS_IN_SECONDS : u32 = 3 * 24 * 60 * 60;
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fn main() {
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println!("
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1/ A constant can be defined outside main,
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and be called from main:
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---RUNNING THE CODE");
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println!("const THREE_DAYS_IN_SECONDS: {THREE_DAYS_IN_SECONDS}
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---END OF EXECUTION");
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println!("
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2/ A variable is mutable only if you use mut. Ex:
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let mut x = 5;
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---RUNNING THE CODE");
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let mut x = 5;
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println!("x (defined by 'let mut') is {x}");
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x = 6;
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println!("x is now {x}
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---END OF EXECUTION");
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println!("
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3/ Instead of allowing mutability,
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a variable can be 'shadowed'.
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It means we redefine a new variable
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on the same namespace. Ex:
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let shadow = 7
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let shadow = shadow + 3
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---RUNNING THE CODE");
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let shadow = 7;
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println!("shadow is {shadow}");
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let shadow = shadow +3;
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println!("shadow is {shadow}");
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{
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let shadow = shadow + 10;
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println!("shadow in scope is {shadow}");
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}
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println!("shadow back outside scope is {shadow}
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---END OF EXECUTION");
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println!("
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4/ shadowing even allows to
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change the type of the variable!
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---RUNNING THE CODE");
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let secret = "xxxx";
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println!("secret is {secret}");
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let secret = secret.len();
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println!("secret - now defined with secret.len() -
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is now: {secret}
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---END OF EXECUTION");
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}
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