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# Variables

In Ride, you can only declare a variable along with a value assignment. The = sign must be followed by an expression. The value of the variable is the expression result.

Ride variables are immutable: the value of a variable cannot be changed after it is defined.

Ride is strongly typed and the variable's type is inferred from the value.

# Lazy Variables

let keyword defines a variable with lazy evaluation: the value of a variable is evaluated the first time it is used.

Examples:

let a = 42                 # Integer variable definition
let b = "Ride the Waves!"  # String variable definition

Ride allows you to define variables globally, inside any function, or even inside a variable definition.

func lazyIsGood() = {
  let c = {
     let d = 1
     true
    }  
  c
}

The function above returns true, but variable d won't be initialized because unused lazy variables are not evaluated.

Since a function is a definition and not an expression, you can assign a function value to a variable but not the function itself.

let result = lazyIsGood()  # result is true

# Strict Variables

strict keyword defines a variable with strict (eager) evaluation. Unlike lazy variables defined with let, a strict variable is evaluated immediately when script execution reaches it, that is, before the next expression.

Strict variable can only be defined only inside another definition, for example, inside the body of a function. A strict variable will not be evaluated if it is defined inside another definition that is not used: for example, inside a function that has not been called.

Strict variables are suitable for dApp-to-dApp invocation as they ensure executing callable functions and applying their actions in the right order. Example:

func foo() = {
   ...
   strict balanceBefore = wavesBalance(this).regular
   strict z = invoke(dapp2,"bar",args,[AttachedPayment(unit,100000000)])
   strict balanceAfter = wavesBalance(this).regular

   if(balanceAfter < balanceBefore) then ... else...
}

In this example, balanceBefore and balanceAfter may differ because payments to dApp2 and actions performed by the bar callable function can affect the balance.

Strict variables are added in Standard library version 5.

# Built-in Variables

The Standard library defines built-in variables that can be used in scripts.

Constant
Function