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Execution conditions

In this exercise, the entry point may only be called by the admin address; it also requires:

  • that the argument value v be between 10 (included) and 20 (strictly)
  • be even

If not even, it must fail with this following message : Expected even value:

2-exec-condition.arl
archetype exec_condition

variable value : nat = 0

constant admin : address = tz1h4CiqWxNe4UxSpkwXy617RM6DaK6NU76P

entry main(v : nat) {
  called by admin
  require {
      r1: 10 <= v < 20;
      r2: v % 2 = 0 otherwise "EXPECTED EVEN VALUE":
  }
  effect {
     value := v;
  }
}

It is also possible to establish execution conditions with a failif section. Execution conditions have identifiers (here r1 and r2) used for fail message when no otherwise is established, and to name the property in contract formal verification.

One of the key requirements of a smart contract's entry point is to establish execution conditions:

  • Who can call the contract?
  • Under which logical conditions?

Archetype provides dedicated syntax to make execution conditions very explicit and non ambiguous.

Deploy

The following Completium CLI command deploys the contract on the Tezos network:

completium-cli deploy 2-exec_condition.arl

Call entry point

The following command calls the unique entry point with the argument 14 using the --with option:

completium-cli call 2-exec_condition --entry main --arg '{ "v" : 14 }'

If the contract call fails with an InvalidCaller error, it is because your tezos test address does not match the admin address specified in the contract code, which proves that the execution condition works as intended. To successfully call the contract, modify the admin address in the code to match your own wallet address, which is listed when you run completium-cli show account. You need to redeploy the contract when making any changes to the code.

View contract

The following command generates the URL to view the contract in Better call Dev:

completium-cli show contract 2-exec-condition

Next

Open '3-rat_transfer.arl' and click on "Next: Rationals & transfers" below.