make inputs a vector to allow variable number of input accounts

risc0-selective-privacy-poc/src/lib.rs

@@ -20,9 +20,8 @@ fn write_inputs<P: Program>(
     instruction_data: &P::InstructionData,
     env_builder: &mut ExecutorEnvBuilder,
 ) -> Result<(), ()> {
-    for account in input_accounts {
-        env_builder.write(&account).map_err(|_| ())?;
-    }
+    let input_accounts = input_accounts.to_vec();
+    env_builder.write(&input_accounts).map_err(|_| ())?;
     env_builder.write(&instruction_data).map_err(|_| ())?;
     Ok(())
 }

risc0-selective-privacy-poc/transfer_methods/guest/src/bin/transfer.rs

@@ -8,10 +8,12 @@ use risc0_zkvm::{
 /// A transfer of balance program.
 /// To be used both in public and private contexts.
 fn main() {
-    let sender: Account = env::read();
-    let receiver: Account = env::read();
+    let mut input_accounts: Vec<Account> = env::read();
     let balance_to_move: u128 = env::read();
 
+    assert_eq!(input_accounts.len(), 2);
+    let [sender, receiver] = input_accounts.try_into().unwrap();
+
     // Check sender has enough balance
     assert!(sender.balance >= balance_to_move);