Questions tagged [haskell]
For Haskell programming questions specifically related to Cardano. For more generic programming questions about Haskell, please consider using Stack Overflow instead.
102
questions
0
votes
1
answer
21
views
Cabal - could not resolve dependencies error
I have completed the pioneer program and am writing my own app. I've created my react front end and now am trying to serialize my smart contract in Haskell for a minting policy I wrote. The problem ...
- 121
0
votes
1
answer
25
views
I am getting error while using "cabal build all" cmd
I am new to plutus. I am trying to learn plutus for which I am using "plutus-starter" code to begin. while using "cabal build" i am getting following error:
Resolving dependencies.....
0
votes
1
answer
16
views
A Simple stack language
I'm working through IOHK Haskell course from 2020, and I'm stuck on problem assignment W3.1, full description linked here:
https://github.com/iohkedu/w03
I do not understand how the instructions type ...
- 47
0
votes
1
answer
31
views
UnsafeFromData instance for custom type
I want to use a custom type for one of my policy parameters, which will be applied by a tool like Lucid.
Example of param:
data CoinParams = CoinParams {
policyOwner :: PubKeyHash,
tokenName ::...
- 135
0
votes
1
answer
18
views
how to use ownPubKey and RedeemerType and DatumType
My code is here.
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE ...
- 21
2
votes
1
answer
18
views
Expecting one more argument to ‘RedeemerType’
My code is here
marketConstraints :: Market -> TxConstraints (RedeemerType -> ScriptContext -> Bool) (DatumType, ())
marketConstraints market = mustValidateIn (to $ scriptAddress market)
I ...
- 21
0
votes
1
answer
23
views
Denied Cabal Access to pictures. Now Getting error
Accidentally denied Cabal Access to pictures through a prompt given. Now, when I try to cabal Init I get this message "User/******/Library/Application Support/MobileSync: getDirectoryContents:...
1
vote
0
answers
30
views
setup a Plutus project use haskell.nix Error on Mac M1
I'm trying to set up a Plutus project with flake on my Macbook by IOHK document
I did the following steps:
create default.nix
enter command nix flake init --template templates#haskell-nix --impure
...
- 11
1
vote
1
answer
48
views
Error when trying to build my Plutus project
I am getting the following error after trying to execute cabal build:
cabal: Could not resolve dependencies:
[__0] next goal: cardano-crypto-class (user goal)
[__0] rejecting: cardano-crypto-class-2.0....
- 1,045
1
vote
1
answer
153
views
How to deploy the Plutus smart contract
I am following Plutus-pioneer-program to learn smart contract development in Cardano. I have tried the onchain and offchain code, compiled and tested in Plutus playground and also in emulator trace. ...
- 19
0
votes
0
answers
79
views
Data from Mesh to Plutus
I created this datum with Mesh
const datumMD: Data = new Map<Data, Data>();
datumMD.set('name', assetName );
datumMD.set('question', input);
datumMD.set('answers', []);
datumMD.set('...
0
votes
0
answers
29
views
Error when running nix-shell on WSL
I'm a newcomer to Cardano trying to learn Plutus. After cloning IOHK's Plutus-apps (https://github.com/input-output-hk/plutus-apps) repo and already installing nix, I found this error when running nix-...
- 31
10
votes
3
answers
251
views
How to properly start a new Plutus project, from scratch
I'm from ETH's ecosystem and recently just decided to get into Cardano development, specifically Plutus dev work thanks to Demeter.Run, and after going through the Plutus starters on there, I noticed ...
- 101
0
votes
1
answer
43
views
Printing a plutus validators cborhex to a file
I was hoping to get some advice re printing a plutus validators cborhex to a file. Im kinda basing my logic off of an example in week03 in the pioneer program but need to make some adaptations.
Below ...
- 25
0
votes
1
answer
26
views
Plutus Playground - mustPayToTheScript - unexpected char escapes - 0 converted to \NUL, 1 to \SOH
I am having trouble with the mustPayToTheScript function - I am getting this error
Contract instance stopped with error: "WalletError (InsufficientFunds \"Total: Value (Map [(,Map [(\\\"...
- 25
3
votes
3
answers
217
views
How to turn (compile) “script.hs” into “script.plutus”?
I have a script that is developed in Plutus Playground. It is working well and now I want to deploy it to the Cardano blockchain via cardano-cli.
Following this answer, I have to use cabal to turn my ...
- 343
1
vote
2
answers
78
views
Plutus playground error when running simulator: WalletContractError ToCardanoError (Tag \"toCardanoPolicyId\" (Tag \"1 bytes\" DeserialisationError))
Plutus-apps v2022-04-06
My smart contract compiles successfully however when i run the simulator i get this error
Contract instance stopped with error: "WalletContractError (ToCardanoError (Tag \&...
- 25
2
votes
3
answers
146
views
Calculate tx fees via Blockfrost or any other provider?
Is there a way to calculate transaction fees without having to go through cardano-cli? Maybe something like Blockfrost? or any other API providers? I don't want to run a local node to do that.
- 421
0
votes
1
answer
66
views
Cardano transaction builder library in Haskell
Is there a way besides cardano-cli that I can use to construct a transaction using Haskell?
Something like Lucid-cardano npm package, but in Haskell land?
Said library should allow me to construct a ...
- 421
4
votes
2
answers
142
views
Why not just simply use Haskell instead of Plutus?
I can think of two major reasons as to why Cardano chose a strongly-typed functional language for it's Blockchain:
Strongly-typed - because as the capabilities of the Blockchain and scripts become ...
- 488
1
vote
0
answers
28
views
How Will the Atala Plutus Integration Work?
I know that Atala prism will be used as the basis of Cardanos DiD but whenever I ask someone how it will work with Plutus, I end up hearing some new infrastructure needs to be built out.
My question ...
- 942
1
vote
1
answer
106
views
How Do You Convert Math Symbols in Haskell?
So i heard you can use denotational semantics to write Haskell code using math notation for example circle in place of . to denote function composition. My question is in four parts:
how do I use/...
- 942
0
votes
1
answer
40
views
Can I Use TraceIfFalse in deployment?
So I use traceIfFalse to test a lot of my smart contracts now I'm ready to deploy some of then and I want to know if this is for development only or if its fine to have a smart contract use this ...
- 942
3
votes
2
answers
65
views
What is Type Safety?
In the Haskell programming language there are a number of concepts that must be understood by anyone wishing to learn and use the maximum potential of the language. One of these what is is type safety....
- 942
0
votes
1
answer
64
views
Cannot wrap my head on NFTs
I am running through the Plutus Pioneer Program and I have reached week 5. Also as a reference, I will use the LobsterChallenge repository. I am a bit confused about how NFTs work for the Cardano ...
1
vote
1
answer
61
views
How do I test my smart-contract on Cardano
I'm from EVM background and I've started learning about Cardano lately. I was just wondering how do I write unit tests for my smart-contract written in Haskell? Since i've been doing unit testing in ...
2
votes
3
answers
79
views
Is there a place where we can find the Haskell library for Marlowe?
I investigated some Code examples, in haskell for Marlowe smart-contract, and used the "cabal repl" with the " :i " command, like this:
*Main> :i ValueEQ
type Observation :: *
...
2
votes
2
answers
54
views
Whats Your Mental Model For Monads?
I was asked by a friend trying to learn plutus what a monad was, so I began talking about category theory. It seems that this confused him further how would you explain monads to a noob?
Whats your ...
- 942
0
votes
1
answer
108
views
Can't create ```TokenName``` using ```tokenName``` with error ```GHC Core to PLC plugin: E042:Error: Unsupported feature: ...```
I'm not sure is relevant but the code in question is for a generic Validator (with Datums and Redeemers) used to get a forwarded minting policy
the problem should be clear from the title, I can't get ...
- 982
0
votes
0
answers
26
views
Tutorial for Haskell Restful-API Webserver
Using free and open source Haskell and with minimal or ideally no external libraries, I need to build a very simple RESTful-API/database server and a CLI to manage it. I need to use it for serving up ...
- 215
0
votes
3
answers
993
views
Installing GHC on WSL
I just installed Ubuntu on WSL for Windows 10 in order to get ready for the Marlowe Pioneers Program. I figure I will need to install GHC and Cabal next in order to install the Cardano-CLI and Marlowe-...
- 215
3
votes
1
answer
62
views
Haskell + Blockfrost toolchain?
I am looking for a Haskell alternative to the cardano-serialization-lib, which can work in conjunction with blockfrost-haskell. So ideally, it should be able to easily create wallet keys, transactions,...
- 73
0
votes
1
answer
17
views
Can someone help to understand how to use handleChainIndexClient?
I'm not guru with Eff system under Haskell.
What i got that method could contains the constraints for monad that should be used with.
module ChainIndexHelper
where
import Plutus.ChainIndex.Client
...
0
votes
1
answer
33
views
How to check whether my two pubkeyHash is different or not using Haskell?
I'm using this script to check but this doesn't works for me
import Prelude hiding (Eq)
mkPolicy :: PubKeyHash -> PubKeyHash -> TokenName -> BuiltinData -> ScriptContext -> Bool
...
0
votes
1
answer
135
views
Cardano DB Sync - RTS Options
After successfully with previous question, where I tried to make cardano-node and cardano-db-sync run as a services, I tried to play around with +RTS ... -RTS option on cardano-db-sync, specifically ...
- 55
0
votes
1
answer
63
views
haskell quite hard [closed]
i'm newbie and trying to learn haskell, but i'm having a problem in the Data.List chapter of learnyouahaskell as follows:
let xs = [1..6] in sum xs / genericLength xs -- > it works
Now I try to ...
1
vote
1
answer
52
views
How to know which module to import?
Let's say my smartcontract needs BuiltinData.
Quicksearch in documentation reveals that BuiltinData is in:
Plutus.V1.Ledger.Api
Plutus.V2.Ledger.Api
PlutusTx.Builtins.Internal
PlutusTx
PlutusTx....
- 569
1
vote
1
answer
57
views
Why is String being interpreted as a type?
According type applications, this extension allows to give explicit type arguments to a polymorphic function.
type VestingSchema =
Endpoint "give" GiveParams
.\/ ...
- 247
-1
votes
1
answer
141
views
Unable to install Gloss on Mac M1
I just learning about Haskell and trying to create Haskell project with Cabal, but when I tried install Gloss, it always return an error
-- error
...
ghc: could not execute: opt
cabal: Failed to build ...
- 9
1
vote
1
answer
242
views
Is type String truly equal to type [Char], and is Haskell truly "pure"?
One fundamental of Haskell is that a string is really a list of characters. Another fundamental is referential transparency, in that a pure function must always give the exact same result when given ...
- 349
0
votes
1
answer
31
views
How to define the return type of `callEndPoint` appropriately?
In homework of week4, I refactored my solution:
payTrace :: Integer -> Integer -> EmulatorTrace ()
payTrace payment1 payment2 = do
contract1 <- activateContractWallet (knownWallet 1) ...
- 172
0
votes
2
answers
27
views
Using `void` vs using `>>` (then) operator
Given a do block which contains these expressions:
void $ submitTx tx
payContract
Would it be feasible to reformat this lines using the then operator, and thus telling the compiler to do something, ...
- 119
1
vote
3
answers
176
views
Please explain types with multiple outputs
I understand basic type signatures like
myFunction :: Int -> String
myFunction a = "Always produce this string"
But in the week 5 lesson, in Free.hs (and similar in the other hs files), ...
- 349
3
votes
2
answers
193
views
Empty TokenName Literal Overloading in Week05 Homework2
This doesn't work
mkPolicy oref () ctx = traceIfFalse "UTxO not consumed" hasUTxO &&
traceIfFalse "wrong amount minted" checkMintedAmount
...
- 125
2
votes
1
answer
51
views
What is a library stanza?
I deduce what stanza definitions are but I was struggling to find an exact definition and explanation why this is used in Haskell/Plutus.
What exactly is a stanza?
Can you compile code Haskell/Plutus ...
- 119
2
votes
1
answer
124
views
Understand purpose of tx-out-datum-hash in Lars' lobster NFT minting example
When the Alonzo era started on mainnet, Lars deployed a smart contract example, in which he minted a lobster NFT as part of a lobster naming challenge.
In the policy script used to mint the lobster ...
- 311
0
votes
2
answers
98
views
Continue to be utterly disoriented as to where these magic words come from and how they might be connected
I continue to be utterly lost as to how to understand the source and ultimately the concrete foundation of this byzantine mass of constructs.
Example. In Lesson 4, in the Contract.hs module (and Trace....
- 349
2
votes
1
answer
84
views
What's the difference between Ledger.CurrencySymbol and Plutus.V1.Ledger.Value.CurrencySymbol?
I'm a bit confused about CurrencySymbol type. In the documentation it appears twice in 2 modules: Plutus.V1.Ledger.Value (first image) and Ledger. (second image)
Are they the same type? When import ...
- 1,294
1
vote
1
answer
94
views
What is the correct way to compare DatumHash?
What is the correct way to compare DatumHash?
I imported the Eq function from PlutusTx
import PlutusTx.Prelude (Eq((==)))
...
checkDatumHash :: TxOut -> Bool
checkDatumHash txOut = ...
- 21
1
vote
1
answer
86
views
Lesson 3 - unsure how "sigs" is created or where txInfoSignatories comes from or how it works
Spoiler Alert!
The solution for lesson 3 includes the following:
{-# INLINABLE mkValidator #-}
-- This should validate if either beneficiary1 has signed the transaction and the current slot is before ...
- 349