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  • Ride Programming Language
    Ride Programming Language
  • Getting Started
    Getting Started
  • Syntax Basics
    • Directives
      Directives
    • Definition
      Definition
    • Expression
      Expression
    • Variable
      Variable
    • Function
      Function
    • Exception
      Exception
    • Comment
      Comment
    Syntax Basics
  • Script Types
    • dApp Script
      • Annotations
        Annotations
      • Callable Function
        Callable Function
      • Verifier Function
        Verifier Function
      dApp Script
    • Account Script
      Account Script
    • Asset Script
      Asset Script
    Script Types
  • Standard Library
    Standard Library
  • Data types
    • Any
      Any
    • BigInt
      BigInt
    • Boolean
      Boolean
    • ByteVector
      ByteVector
    • Int
      Int
    • String
      String
    • Unit
      Unit
    • List
      List
    • Tuple
      Tuple
    • Union
      Union
    Data types
  • Structures
    • Script Actions
      • BinaryEntry
        BinaryEntry
      • BooleanEntry
        BooleanEntry
      • Burn
        Burn
      • DeleteEntry
        DeleteEntry
      • IntegerEntry
        IntegerEntry
      • Issue
        Issue
      • Lease
        Lease
      • LeaseCancel
        LeaseCancel
      • Reissue
        Reissue
      • ScriptTransfer
        ScriptTransfer
      • SponsorFee
        SponsorFee
      • StringEntry
        StringEntry
      Script Actions
    • Common Structures
      • Address
        Address
      • Alias
        Alias
      • Asset
        Asset
      • AssetPair
        AssetPair
      • AttachedPayment
        AttachedPayment
      • BalanceDetails
        BalanceDetails
      • BlockInfo
        BlockInfo
      • Invocation
        Invocation
      • Order
        Order
      • Transfer
        Transfer
      Common Structures
    • Transaction Structures
      • BurnTransaction
        BurnTransaction
      • CreateAliasTransaction
        CreateAliasTransaction
      • DataTransaction
        DataTransaction
      • ExchangeTransaction
        ExchangeTransaction
      • GenesisTransaction
        GenesisTransaction
      • InvokeScriptTransaction
        InvokeScriptTransaction
      • IssueTransaction
        IssueTransaction
      • LeaseCancelTransaction
        LeaseCancelTransaction
      • LeaseTransaction
        LeaseTransaction
      • MassTransferTransaction
        MassTransferTransaction
      • ReissueTransaction
        ReissueTransaction
      • SetAssetScriptTransaction
        SetAssetScriptTransaction
      • SetScriptTransaction
        SetScriptTransaction
      • SponsorFeeTransaction
        SponsorFeeTransaction
      • TransferTransaction
        TransferTransaction
      • UpdateAssetInfoTransaction
        UpdateAssetInfoTransaction
      Transaction Structures
    Structures
  • Built-in Variables
    Built-in Variables
  • Built-in Functions
    • Account Data Storage Functions
      Account Data Storage Functions
    • Blockchain Functions
      Blockchain Functions
    • Byte Array Functions
      Byte Array Functions
    • Converting Functions
      Converting Functions
    • dApp-to-dApp Invocation Function
      dApp-to-dApp Invocation Function
    • Data Transaction Functions
      Data Transaction Functions
    • Decoding Functions
      Decoding Functions
    • Encoding Functions
      Encoding Functions
    • Exception Functions
      Exception Functions
    • Hashing Functions
      Hashing Functions
    • List Functions
      List Functions
    • Math Functions
      Math Functions
    • String Functions
      String Functions
    • Union Functions
      Union Functions
    • Verification Functions
      Verification Functions
    Built-in Functions
  • Operators
    Operators
  • match ... case: Pattern Matching
    match ... case: Pattern Matching
  • Iterations with FOLD<N>
    Iterations with FOLD<N>
  • dApp-to-dApp Invocation
    dApp-to-dApp Invocation
  • Limitations
    • Complexity
      Complexity
    • Data Weight
      Data Weight
    Limitations
  • Previous Versions
    • Version 5
      • Callable Function
        Callable Function
      • Data types
        • Any
          Any
        • BigInt
          BigInt
        • Boolean
          Boolean
        • ByteVector
          ByteVector
        • Int
          Int
        • String
          String
        • Unit
          Unit
        • List
          List
        • Tuple
          Tuple
        • Union
          Union
        Data types
      • Structures
        • Script Actions
          • BinaryEntry
            BinaryEntry
          • BooleanEntry
            BooleanEntry
          • Burn
            Burn
          • DeleteEntry
            DeleteEntry
          • IntegerEntry
            IntegerEntry
          • Issue
            Issue
          • Lease
            Lease
          • LeaseCancel
            LeaseCancel
          • Reissue
            Reissue
          • ScriptTransfer
            ScriptTransfer
          • SponsorFee
            SponsorFee
          • StringEntry
            StringEntry
          Script Actions
        • Common Structures
          • Address
            Address
          • Alias
            Alias
          • Asset
            Asset
          • AssetPair
            AssetPair
          • AttachedPayment
            AttachedPayment
          • BalanceDetails
            BalanceDetails
          • BlockInfo
            BlockInfo
          • Invocation
            Invocation
          • Order
            Order
          • Transfer
            Transfer
          Common Structures
        • Transaction Structures
          • BurnTransaction
            BurnTransaction
          • CreateAliasTransaction
            CreateAliasTransaction
          • DataTransaction
            DataTransaction
          • ExchangeTransaction
            ExchangeTransaction
          • GenesisTransaction
            GenesisTransaction
          • InvokeScriptTransaction
            InvokeScriptTransaction
          • IssueTransaction
            IssueTransaction
          • LeaseCancelTransaction
            LeaseCancelTransaction
          • LeaseTransaction
            LeaseTransaction
          • MassTransferTransaction
            MassTransferTransaction
          • ReissueTransaction
            ReissueTransaction
          • SetAssetScriptTransaction
            SetAssetScriptTransaction
          • SetScriptTransaction
            SetScriptTransaction
          • SponsorFeeTransaction
            SponsorFeeTransaction
          • TransferTransaction
            TransferTransaction
          • UpdateAssetInfoTransaction
            UpdateAssetInfoTransaction
          Transaction Structures
        Structures
      • Built-in Variables
        Built-in Variables
      • Built-in Functions
        • Account Data Storage Functions
          Account Data Storage Functions
        • Blockchain Functions
          Blockchain Functions
        • Byte Array Functions
          Byte Array Functions
        • Converting Functions
          Converting Functions
        • dApp-to-dApp Invocation Function
          dApp-to-dApp Invocation Function
        • Data Transaction Functions
          Data Transaction Functions
        • Decoding Functions
          Decoding Functions
        • Encoding Functions
          Encoding Functions
        • Exception Functions
          Exception Functions
        • Hashing Functions
          Hashing Functions
        • List Functions
          List Functions
        • Math Functions
          Math Functions
        • String Functions
          String Functions
        • Union Functions
          Union Functions
        • Verification Functions
          Verification Functions
        Built-in Functions
      • Operators
        Operators
      • Limitations
        • Data Weight
          Data Weight
        Limitations
      Version 5
    • Version 4 and 3
      • Callable Function
        Callable Function
      • Data types
        • Boolean
          Boolean
        • ByteVector
          ByteVector
        • Int
          Int
        • String
          String
        • Unit
          Unit
        • List
          List
        • Tuple
          Tuple
        • Union
          Union
        Data types
      • Structures
        • Script Actions
          • BinaryEntry (v4)
            BinaryEntry (v4)
          • BooleanEntry (v4)
            BooleanEntry (v4)
          • Burn (v4)
            Burn (v4)
          • DataEntry (v3)
            DataEntry (v3)
          • DeleteEntry (v4)
            DeleteEntry (v4)
          • IntegerEntry (v4)
            IntegerEntry (v4)
          • Issue (v4)
            Issue (v4)
          • Reissue (v4)
            Reissue (v4)
          • ScriptTransfer (v3 and v4)
            ScriptTransfer (v3 and v4)
          • SponsorFee (v4)
            SponsorFee (v4)
          • StringEntry (v4)
            StringEntry (v4)
          Script Actions
        • Script Results (v3)
          • ScriptResult
            ScriptResult
          • TransferSet
            TransferSet
          • WriteSet
            WriteSet
          Script Results (v3)
        • Common Structures
          • Address
            Address
          • Alias
            Alias
          • Asset
            Asset
          • AssetPair
            AssetPair
          • AttachedPayment
            AttachedPayment
          • BalanceDetails
            BalanceDetails
          • BlockInfo
            BlockInfo
          • Invocation
            Invocation
          • Order
            Order
          • Transfer
            Transfer
          Common Structures
        • Transaction Structures
          • BurnTransaction
            BurnTransaction
          • CreateAliasTransaction
            CreateAliasTransaction
          • DataTransaction
            DataTransaction
          • ExchangeTransaction
            ExchangeTransaction
          • GenesisTransaction
            GenesisTransaction
          • InvokeScriptTransaction
            InvokeScriptTransaction
          • IssueTransaction
            IssueTransaction
          • LeaseCancelTransaction
            LeaseCancelTransaction
          • LeaseTransaction
            LeaseTransaction
          • MassTransferTransaction
            MassTransferTransaction
          • ReissueTransaction
            ReissueTransaction
          • SetAssetScriptTransaction
            SetAssetScriptTransaction
          • SetScriptTransaction
            SetScriptTransaction
          • SponsorFeeTransaction
            SponsorFeeTransaction
          • TransferTransaction
            TransferTransaction
          • UpdateAssetInfoTransaction
            UpdateAssetInfoTransaction
          Transaction Structures
        Structures
      • Built-in Variables
        Built-in Variables
      • Built-in Functions
        • Account Data Storage Functions
          Account Data Storage Functions
        • Blockchain Functions
          Blockchain Functions
        • Byte Array Functions
          Byte Array Functions
        • Converting Functions
          Converting Functions
        • Data Transaction Functions
          Data Transaction Functions
        • Decoding Functions
          Decoding Functions
        • Encoding Functions
          Encoding Functions
        • Exception Functions
          Exception Functions
        • Hashing Functions
          Hashing Functions
        • List Functions
          List Functions
        • Math Functions
          Math Functions
        • String Functions
          String Functions
        • Union Functions
          Union Functions
        • Verification Functions
          Verification Functions
        Built-in Functions
      • Operators
        Operators
      • Limitations
        • Data Weight
          Data Weight
        Limitations
      Version 4 and 3
    Previous Versions
  • Import Libraries
    Import Libraries
  • Ride Components
    Ride Components
      • English
      • Русский
      On this page
        • Lazy Variables
        • Strict Variables
      waves_logo Docs

          # 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 variable is not evaluated immediately, but only the first time the variable is used.

          Examples:

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

          You can 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 evaluated because unused lazy variables are not evaluated.

          Note that lazy variables are evaluated not in the same order they are defined, but in the order they are used.

          # don't do this
          func foo() = {
             ...
             let balanceBefore = wavesBalance(this).regular
             let result = invoke(dApp2,"bar",args,[AttachedPayment(unit,100000000)])
             let balanceAfter = wavesBalance(this).regular
          
             if(balanceAfter < balanceBefore) then ... else...
          }
          

          In this example, balanceAfter would be evaluated before balanceBefore, and their values would be the same. invoke() won't be called at all.

          # 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 result = invoke(dApp2,"bar",args,[AttachedPayment(unit,100000000)])
             strict balanceAfter = wavesBalance(this).regular
          
             if(balanceAfter < balanceBefore) then ... else...
          }
          

          This example evaluates balanceBefore first, then result with a call to invoke(), then balanceAfter. The values of balanceBefore and balanceAfter may differ because payments to dApp2 and actions performed by the bar callable function affect the balance.

          Note that using lazy and strict variables together can have unexpected effects. Example:

          # don't do this
          {-# STDLIB_VERSION 6 #-}
          {-# CONTENT_TYPE DAPP #-}
          {-# SCRIPT_TYPE ACCOUNT #-}
          
          let lpTokenId = base58'...'
          let rewardTokenId = base58'...'
          
          @Callable(i)
          func burn(amount: Int) = [ Burn(lpTokenId, amount) ]
          
          @Callable(i)
          func reward() = {
             let p = value(i.payments[0])
             if p.assetId != lpTokenId
                then throw("Incorrect payment")
                else {
                   let lpQty = assetInfo(lpTokenId).value().quantity
                   let rewardQty = assetInfo(rewardTokenId).value().quantity
                   let share = fraction(p.amount,rewardQty,lpQty)
                   strict result = invoke(this, "burn", [p.amount], [])
                   [
                      ScriptTransfer(i.caller, share, rewardTokenId)
                   ]
                }
          }
          

          The share variable is lazy, so the reward() function first calls the burn() function and then evaluates share. For example, if there are 100 LP tokens in total and a user attached 20 of them to the script invocation, then 20 LP tokens are burned first, then the share (20 LP tokens of the remaining 80) is calculated. As a result, the user receive not 20%, but 25% of the total quantity of the reward token.

          Strict variables are added in Standard library version 5.

          # Built-in Variables

          The Standard library defines built-in variables that you can use in scripts.

          Expression
          Function
          Expression
          Function