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Aleo Programs

An Aleo program defines private application logic executed by the Aleo VM. Most developers write programs in Leo and compile them for the VM.

Structure​

  • Program ID: program <name>.aleo;
  • Entrypoints: typed inputs → computation → typed outputs
  • Types: primitives plus struct and record
program foo.aleo;

function hello:
    input r0 as u32.public;
    input r1 as u32.private;
    add r0 r1 into r2;
    output r2 as u32.private;

Registers and visibility​

Values are stored in registers (r0, r1, ...). Each value has a type and a visibility:

  • .public: revealed
  • .private: proven, not revealed

Types​

Primitive types include:

address
boolean
field
group
i8
i16
i32
i64
i128
u8
u16
u32
u64
u128
scalar

struct​

struct array3:
    a0 as u32;
    a1 as u32;
    a2 as u32;

record (private state)​

Records are user-owned state. Transactions typically consume records and create new records.

record token:
    owner as address.private;
    amount as u64.private;

Example: mint + transfer​

program foo.aleo;

record token:
    owner as address.private;
    amount as u64.private;

function mint:
    input r0 as u64.private;
    cast self.signer r0 into r1 as token.record;
    output r1 as token.record;

function transfer_amount:
    input r0 as token.record;
    input r1 as address.private;
    input r2 as u64.private;

    sub r0.amount r2 into r3;
    cast r0.owner r3 into r4 as token.record;
    cast r1 r2 into r5 as token.record;
    output r4 as token.record;
    output r5 as token.record;

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