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Some cleanup
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d0cd committed Jul 28, 2024
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210 changes: 100 additions & 110 deletions documentation/leo/03_language.md
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Expand Up @@ -288,9 +288,9 @@ record token {

### Array

Leo supports static arrays. Arrays are declared as `[type; length]` and can be nested. Arrays cannot be empty nor modified.
Leo supports static arrays. Array types are declared as `[type; length]` and can be nested. Arrays cannot be empty nor modified.

Arrays only support constant accesses (the index must be a constant value). The accessor value must be a constant integer.
Arrays only support constant accesses. The accessor expression must be a constant integer.

Arrays can contain primitive data types, structs, or arrays. Structs and records can also contain arrays.

Expand All @@ -300,14 +300,14 @@ Arrays can be iterated over using a for loop.
// Initalize a boolean array of length 4
let arr: [bool; 4] = [true, false, true, false];
// Nested Array
// Nested array
let nested: [[bool; 2]; 2] = [[true, false], [true, false]];
// Array of Structs
struct bar {
data: u8,
}
// Array of structs
let arr_of_structs: [bar; 2] = [bar { data: 1u8 }, bar { data: 2u8 }];
// Access the field of a struct within an array
Expand All @@ -326,7 +326,7 @@ record floo {
data: [u8; 8],
}
// Declare a mapping that contains an array value
// Declare a mapping that contains array values
mapping data: address => [bool; 8];
// Iterate over an array using a for loop and sum the values within
Expand All @@ -341,7 +341,7 @@ transition sum_with_loop(a: [u64; 4]) -> u64 {

### Tuple

Leo supports tuples. Tuples are declared as `(type1, type2, ...)` and can be nested. Tuples cannot be empty nor modified.
Leo supports tuples. Tuple types are declared as `(type1, type2, ...)` and can be nested. Tuples cannot be empty or modified.

Tuples only support constant access with a dot `.` and a constant integer.

Expand Down Expand Up @@ -378,7 +378,7 @@ program hello.aleo {

#### Function Inputs

A function input is declared as `{visibility} {name}: {type},`
A function input is declared as `{visibility} {name}: {type}`.
Function inputs must be declared just after the function name declaration, in parentheses.

```leo showLineNumbers
Expand All @@ -401,11 +401,11 @@ transition foo(public a: field) -> field {

### Helper Function

A helper function is declared as `function {name}() {}`.
A helper function is declared as `function {name}({arguments}) {}`.
Helper functions contain expressions and statements that can compute values,
however helper functions cannot produce `records`.

Helper functions cannot be called directly from the outside. Instead, they must be called by other functions.
Helper functions cannot be called directly. Instead, they must be called by other functions.
Inputs of helper functions cannot have `{visibility}` modifiers like transition functions,
since they are used only internally, not as part of a program's external interface.

Expand Down Expand Up @@ -439,11 +439,11 @@ inline foo(

The rules for functions (in the traditional sense) are as follows:

- There are three variants of functions: transition, function, inline.
- transitions can only call functions and inlines.
- functions can only call inlines.
- inlines can only call inlines.
- Direct/indirect recursive calls are not allowed
- There are three variants of functions: `transition`, `function`, `inline`.
- A `transition` can only call a `function`, `inline`, or external `transition`.
- A `function` can only call an `inline`.
- An `inline` can only call another `inline`.
- Direct/indirect recursive calls are not allowed.

### Async Function

Expand All @@ -463,9 +463,9 @@ program transfer.aleo {
// from `account` into a token record for the specified receiver.
//
// This function preserves privacy for the receiver's record, however
// it publicly reveals the caller and the specified token amount.
// it publicly reveals the sender and the specified token amount.
async transition transfer_public_to_private(
public receiver: address,
receiver: address,
public amount: u64
) -> (token, Future) {
// Produce a token record for the token receiver.
Expand Down Expand Up @@ -493,7 +493,7 @@ program transfer.aleo {

If there is no need to create or alter the public on-chain state, async functions are not required.

### Mapping
### Mappings

A mapping is declared as `mapping {name}: {key-type} => {value-type}`.
Mappings contain key-value pairs.
Expand All @@ -508,8 +508,39 @@ mapping account: address => u64;

#### Mapping Operations

The mapping struct allows the programmer to apply updates to a program mapping data structure by calling one of the
following functions.
Mappings can be read from and modified by calling one of the following functions.



#### get

A get command, e.g. `current_value = Mapping::get(counter, addr);`
Gets the value stored at `addr` in `counter` and stores the result in `current_value`
If the value at `addr` does not exist, then the program will fail to execute.

#### get_or_use

A get command that uses the provided default if the key is not present in the mapping,
e.g. `let current_value: u64 = Mapping::get_or_use(counter, addr, 0u64);`
Gets the value stored at `addr` in `counter` and stores the result in `current_value`.
If the key is not present, `0u64` is stored in `counter` (associated to the key) and in `current_value`.

#### set

A set command, e.g. `Mapping::set(counter, addr, current_value + 1u64);`
Sets the `addr` entry as `current_value + 1u64` in `counter`.

#### contains

A contains command, e.g. `let contains: bool = Mapping::contains(counter, addr);`
Returns `true` if `addr` is present in `counter`, `false` otherwise.

#### remove

A remove command, e.g. `Mapping::remove(counter, addr);`
Removes the entry at `addr` in `counter`.

#### Usage

:::info
Mapping operations are only allowed in an [async function](#async-function).
Expand All @@ -532,42 +563,47 @@ program test.aleo {
}
```
## Control Structures

#### get

A get command, e.g. `current_value = Mapping::get(counter, addr);`
Gets the value stored at `addr` in `counter` and stores the result in `current_value`
If the value at `addr` does not exist, then the program will fail to execute.

#### get_or_use
### If Statements

A get command that uses the provided default in case of failure,
e.g. `let current_value: u64 = Mapping::get_or_use(counter, addr, 0u64);`
Gets the value stored at `addr` in `counter` and stores the result in `current_value`.
If the key is not present, `0u64` is stored in `counter` and stored in `current_value`.
If statements are declared as `if {condition} { ... } else if {condition} { ... } else { ... }`.
If statements can be nested.

#### set

A set command, e.g. `Mapping::set(counter, addr, current_value + 1u64);`
Sets the `addr` entry as `current_value + 1u64` in `counter`.
```leo
let a: u8 = 1u8;
if a == 1u8 {
a += 1u8;
} else if a == 2u8 {
a += 2u8;
} else {
a += 3u8;
}
```

#### contains
### Return Statements

A contains command, e.g. `let contains: bool = Mapping::contains(counter, addr);`
Returns `true` if `addr` is present in `counter`, `false` otherwise.
Return statements are declared as `return {expression};`.

#### remove
```leo
let a: u8 = 1u8;
if a == 1u8 {
return a + 1u8;
} else if a == 2u8 {
return a + 2u8;
} else {
return a + 3u8;
}
```

A remove command, e.g. `Mapping::remove(counter, addr);`
Removes the entry at `addr` in `counter`.

## For Loops
### For Loops

For Loops are declared as `for {variable: type} in {lower bound}..{upper bound}`. Unsigned integer
types `u8`, `u16`, and `u32` are recommended for loop variable types. The lower bound must be
For loops are declared as `for {variable: type} in {lower bound}..{upper bound}`. The loop bounds must be integer types and constant. Furthermore, the lower bound must be
less than the upper bound. Nested loops are supported.

### Example

```leo
let count: u32 = 0u32;
Expand All @@ -582,13 +618,11 @@ less than the upper bound. Nested loops are supported.
## Operators

Operators in Leo compute a value based off of one or more expressions.
Leo will try to detect arithmetic operation errors as soon as possible.
If an integer overflow or division by zero can be identified at compile time, Leo will quickly tell the programmer.
Otherwise, the error will be caught at proving time when transition function inputs are processed.
Leo defaults to checked arithmetic, which means that it will throw an error if an overflow or division by zero is detected.

For instance, addition adds `first` with `second`, storing the outcome in `destination`.
For integer types, a constraint is added to check for overflow.
For cases where wrapping semantics are needed for integer types, see the `Add Wrapped` operator.
For cases where wrapping semantics are needed for integer types, see the wrapped variants of the operators.

```leo
let a: u8 = 1u8 + 1u8;
Expand All @@ -601,59 +635,7 @@ a = a.add(1u8);
// a is now equal to 4
```

### Arithmetic Operators

| Operation | Operands | Supported Types |
| :--------------------------------------------------------------------------: | :-----------------: | :----------------------------------------------------------------------------------: |
| addition | `+` `+=` `.add()` | `field` `group` `scalar` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| wrapping addition | `.add_wrapped()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| negation(unary) | `-` `.neg()` | `field` `group` `i8` `i16` `i32` `i64` `i128` |
| subtraction(binary) | `-` `-=` `.sub()` | `field` `group` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| wrapping subtraction(binary) | `.sub_wrapped()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| multiplication | `*` `*=` `.mul()` | `field` `group` `scalar` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| wrapping multiplication | `.mul_wrapped()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| division | `/` `/=` `.div()` | `field` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| wrapping division | `.div_wrapped()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| remainder | `%` `%=` `.rem()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| wrapping remainder | `.rem_wrapped()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| exponentiation | `**` `**=` `.pow()` | `field` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| wrapping exponentiation | `.pow_wrapped()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| [left shift](https://developer.aleo.org/leo/operators#shl) | `<<` `<<=` `.shl()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| [wrapping left shift](https://developer.aleo.org/leo/operators#shl_wrapped) | `.shl_wrapped()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| [right shift](https://developer.aleo.org/leo/operators#shr) | `>>` `>>=` `.shr()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| [wrapping right shift](https://developer.aleo.org/leo/operators#shr_wrapped) | `.shr_wrapped()` | `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| absolute value | `.abs()` | `i8` `i16` `i32` `i64` `i128` |
| wrapping absolute value | `.abs_wrapped()` | `i8` `i16` `i32` `i64` `i128` |
| doubling | `.double()` | `field` `group` |
| squaring | `.square()` | `field` |
| square root | `.square_root()` | `field` |
| inverse | `.square_root()` | `field` |

### Logical Operators

| Operation | Operands | Supported Types |
| :-------------: | :----------------------------------------------: | :----------------------------------------------------------------: |
| NOT | `!` `.not()` | `bool` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| AND | `&` `&=` `.and()` | `bool` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| OR | <code>&#124;</code> <code>&#124;=</code> `.or()` | `bool` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| XOR | `^` `^=` `.xor()` | `bool` `i8` `i16` `i32` `i64` `i128` `u8` `u16` `u32` `u64` `u128` |
| NAND | `.nand()` | `bool` |
| NOR | `.nor()` | `bool` |
| conditional AND | `&&` | `bool` |
| conditional OR | <code>&#124;&#124;</code> | `bool` |

### Relational Operators

Relational operators will always resolve to a boolean `bool` value.

| Operation | Operands | Supported Types |
| :-------------------: | :-----------: | :-------------------------------------------------------------: |
| equal | `==` `.eq()` | `bool`, `group`, `field`, integers, addresses, structs, records |
| not-equal | `!=` `.neq()` | `bool`, `group`, `field`, integers, addresses, structs, records |
| less than | `<` `.lt()` | `field`, `scalar`, integers |
| less than or equal | `<=` `.lte()` | `field`, `scalar`, integers |
| greater than | `>` `.gt()` | `field`, `scalar`, integers |
| greater than or equal | `>=` `.gte()` | `field`, `scalar`, integers |
See the [Operator Reference](./04_operators.md) for a complete list of operators.

### Operator Precedence

Expand Down Expand Up @@ -685,17 +667,13 @@ let result = (a + 1u8) * 2u8;

`(a + 1u8)` will be evaluated before multiplying by two `* 2u8`.

## Commands
## Context-dependent Expressions

Leo supports several commands that can be used to reference information about the Aleo blockchain and the current transaction.
Leo supports several expressions that can be used to reference information about the Aleo blockchain and the current transaction.

### self.caller

:::note
`self.caller` is currently implemented as `self.signer` within Aleo instructions. This will be fixed in a upcoming release.
:::

Returns the address of the account that is calling the program function.
Returns the address of the account/program that invoked the current `transition`.

```leo showLineNumbers
program test.aleo {
Expand All @@ -705,6 +683,18 @@ program test.aleo {
}
```

### self.signer

Returns the address of the account that invoked that top-level `transition`. This is the account that signed the transaction.

```leo showLineNumbers
program test.aleo {
transition matches(addr: address) -> bool {
return self.signer == addr;
}
}
```

### block.height

Returns the height of the current block.
Expand All @@ -728,7 +718,7 @@ program test.aleo {
## Core Functions

Core functions are functions that are built into the Leo language.
They are used to perform cryptographic operations such as hashing, commitment, and random number generation.
They are used to check assertions and perform cryptographic operations such as hashing, commitment, and random number generation.

### Assert and AssertEq

Expand All @@ -747,7 +737,7 @@ program test.aleo {
### Hash

Leo supports the following hashing algorithms: `BHP256`, `BHP512`, `BHP768`, `BHP1024`, `Pedersen64`, `Pedersen128`, `Poseidon2`, `Poseidon4`, `Poseidon8`, `Keccak256`, `Keccak384`, `Keccak512`, `SHA3_256`, `SHA3_384`, `SHA3_512`.
The output type of a commitment function is specified in the function name. e.g. `hash_to_group` will return a `group` type.
The output type of a hash function is specified in the function name. e.g. `hash_to_group` will return a `group` type.
Hash functions take any type as an argument.

```leo showLineNumbers
Expand Down
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