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README.md
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README.md
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# The Leo Programming Language
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[![Build Status](https://travis-ci.com/AleoHQ/leo.svg?token=Xy7ht9JdPvr4xSgbPruF&branch=master)](https://travis-ci.com/AleoHQ/leo)
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![CI](https://github.com/AleoHQ/leo/workflows/CI/badge.svg)
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[![codecov](https://codecov.io/gh/AleoHQ/leo/branch/master/graph/badge.svg?token=S6MWO60SYL)](https://codecov.io/gh/AleoHQ/leo)
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## Compiler Architecture
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@ -43,8 +43,8 @@ Leo supports `let` and `const` keywords for variable definition.
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**Constant** variables do not define a variable in the constraint system. Their value is constrained in the circuit on computation with an **allocated** variable.
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**Constant** variables cannot be mutable. They have the same functionality as `const` variables in other languages.
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```rust
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function addOne() -> {
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```js
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function add_one() -> {
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let a = 0u8; // allocated, value enforced on this line
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const b = 1u8; // constant, value not enforced yet
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@ -57,7 +57,7 @@ Computations are expressed in terms of arithmetic circuits, in particular rank-1
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* All defined variables in Leo are immutable by default.
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* Variables can be made mutable with the `mut` keyword.
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```rust
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```js
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function main() {
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let a = 0u32;
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//a = 1 <- Will fail
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@ -67,10 +67,20 @@ function main() {
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}
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```
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## Addresses
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Addresses are defined to enable compiler-optimized routines for parsing and operating over addresses. These semantics will be accompanied by a standard library in a future sprint.
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```js
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function main() {
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let sender = address(aleo1qnr4dkkvkgfqph0vzc3y6z2eu975wnpz2925ntjccd5cfqxtyu8sta57j8);
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}
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```
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## Booleans
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Explicit types are optional.
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```rust
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```js
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function main() -> bool {
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let a: bool = true || false;
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let b = false && false;
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@ -87,7 +97,7 @@ function main() -> bool {
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### Integers
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Supported integer types: `u8`, `u16`, `u32`, `u64`, `u128`
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```rust
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```js
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function main() -> u32 {
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let a = 2u32; // explicit type
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let a: u32 = 1 + 1; // explicit type
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@ -101,7 +111,7 @@ function main() -> u32 {
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```
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### Field Elements
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```rust
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```js
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function main() -> field {
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let a = 1000field; // explicit type
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let a: field = 21888242871839275222246405745257275088548364400416034343698204186575808495617; // explicit type
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@ -113,11 +123,11 @@ function main() -> field {
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}
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```
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### Affine Points
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The set of affine points on the elliptic curve passed into the leo compiler forms a group.
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### Group Elements
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An affine point on the elliptic curve passed into the Leo compiler forms a group.
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Leo supports this set as a primitive data type.
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```rust
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```js
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function main() -> group {
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let a = 1000group; // explicit type
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let a = (21888242871839275222246405745257275088548364400416034343698204186575808495617, 21888242871839275222246405745257275088548364400416034343698204186575808495617)group; // explicit type
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@ -128,7 +138,7 @@ function main() -> group {
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```
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### Operator Assignment Statements
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```rust
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```js
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function main() -> u32 {
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let mut a = 10;
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a += 5;
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@ -143,7 +153,7 @@ function main() -> u32 {
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## Arrays
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Leo supports static arrays with fixed length.
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```rust
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```js
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function main() -> u32[2] {
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// initialize an integer array with integer values
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let mut a: u32[3] = [1, 2, 3];
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@ -171,7 +181,7 @@ function main() -> u32[2] {
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```
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### Multidimensional Arrays
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```rust
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```js
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function main() -> u32[3][2] {
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let m = [[0u32, 0u32], [0u32, 0u32]];
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@ -191,7 +201,7 @@ Ternary `if [cond] ? [first] : [second];` expressions are the cheapest form of c
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Since `first` and `second` are expressions, we can resolve their values before proceeding execution.
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In the underlying circuit, this is a single bit multiplexer.
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```rust
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```js
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function main() -> u32 {
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let y = if 3==3 ? 1 : 5;
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return y
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@ -202,7 +212,7 @@ function main() -> u32 {
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Leo supports the traditional `if [cond] { [first] } else { [second] }` which can be chained using `else if`.
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Since `first` and `second` are one or more statements, they resolve to separate circuits which will all be evaluated.
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In the underlying circuit this can be thought of as a demultiplexer.
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```rust
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```js
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function main(a: bool, b: bool) -> u32 {
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let mut res = 0u32;
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if a {
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@ -217,7 +227,7 @@ function main(a: bool, b: bool) -> u32 {
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```
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### For loop
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```rust
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```js
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function main() -> fe {
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let mut a = 1field;
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for i in 0..4 {
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@ -228,7 +238,7 @@ function main() -> fe {
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```
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## Functions
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```rust
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```js
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function test1(a : u32) -> u32 {
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return a + 1
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}
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@ -248,7 +258,7 @@ function main() -> u32 {
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### Function Scope
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```rust
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```js
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function foo() -> field {
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// return myGlobal <- not allowed
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return 42field
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@ -262,7 +272,7 @@ function main() -> field {
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### Multiple returns
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Functions can return tuples whose types are specified in the function signature.
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```rust
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```js
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function test() -> (u32, u32[2]) {
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return 1, [2, 3]
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}
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### Function inputs
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Main function inputs are allocated private variables in the program's constraint system.
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`a` is implicitly private.
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```rust
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```js
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function main(a: field) -> field {
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return a
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}
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```
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Normal function inputs are passed by value.
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```rust
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```js
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function test(mut a: u32) {
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a = 0;
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}
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@ -301,7 +311,7 @@ Circuits in Leo are similar to classes in object oriented langauges. Circuits ar
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Members can be defined as fields which hold primitive values
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```rust
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```js
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circuit Point {
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x: u32
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y: u32
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```
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Members can also be defined as functions.
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```rust
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circuit Circ {
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```js
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circuit Foo {
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function echo(x: u32) -> u32 {
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return x
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}
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}
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function main() -> u32 {
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let c = Circ { };
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let c = Foo { };
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return c.echo(1u32)
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}
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```
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Circuit functions can be made static, enabling them to be called without instantiation.
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```rust
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circuit Circ {
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```js
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circuit Foo {
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static function echo(x: u32) -> u32 {
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return x
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}
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}
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function main() -> u32 {
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return Circ::echo(1u32)
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return Foo::echo(1u32)
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}
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```
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The `Self` keyword is supported in circuit functions.
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```rust
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```js
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circuit Circ {
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b: bool
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@ -358,19 +368,19 @@ function main() -> Circ {
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## Imports
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Leo supports importing functions and circuits by name into the current file with the following syntax:
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```rust
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```js
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import [package].[name];
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```
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#### Import Aliases
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To import a name using an alias:
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```rust
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```js
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import [package].[name] as [alias];
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```
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#### Import Multiple
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To import multiple names from the same package:
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```rust
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```js
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import [package].(
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[name_1],
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[name_2] as [alias],
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@ -380,20 +390,20 @@ import [package].(
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#### Import Star
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To import all symbols from a package:
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Note that this will only import symbols from the package library `lib.leo` file.
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```rust
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```js
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import [package].*;
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```
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### Local
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You can import from a local file in the `src/` directory by using its `[file].leo` as the `[package]` name.
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```rust
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```js
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import [file].[name];
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```
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#### Example:
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`src/bar.leo`
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```rust
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```js
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circuit Bar {
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b: u32
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}
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@ -404,7 +414,7 @@ function baz() -> u32 {
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```
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`src/main.leo`
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```rust
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```js
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import bar.(
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Bar,
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baz
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### Foreign
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You can import from a foreign package in the `imports/` directory using its `[package]` name.
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```rust
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```js
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import [package].[name];
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```
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#### Example:
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`imports/bar/src/lib.leo`
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```rust
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```js
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circuit Bar {
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b: u32
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}
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```
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`src/main.leo`
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```rust
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```js
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import bar.Bar;
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function main() {
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@ -441,7 +451,7 @@ function main() {
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### Package Paths
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Leo treats directories as package names when importing.
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```rust
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```js
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import [package].[directory].[file].[name]
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```
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@ -450,14 +460,14 @@ We wish to import the `Baz` circuit from the `baz.leo` file in the `bar` directo
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`imports/foo/src/bar/baz.leo`
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```rust
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```js
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circuit Baz {
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b: u32
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}
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```
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`src/main.leo`
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```rust
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```js
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import foo.bar.baz.Baz;
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function main() {
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@ -470,7 +480,7 @@ function main() {
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### Assert Equals
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This will enforce that the two values are equal in the constraint system.
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```rust
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```js
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function main() {
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assert_eq!(45, 45);
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@ -484,7 +494,7 @@ function main() {
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Use the `test` keyword to add tests to a leo program. Tests must have 0 function inputs and 0 function returns.
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```rust
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```js
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function main(a: u32) -> u32 {
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return a
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}
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