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Refactor expansion interpreter #33

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Refactor expansion interpreter #33

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8037bc6
Replace `next!` with a `next_item` function
SabrinaJewson Mar 30, 2023
92da167
Remove use of loop labels
SabrinaJewson Mar 30, 2023
6145512
Extract binary and unary evaluation to a function
SabrinaJewson Mar 30, 2023
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137 changes: 70 additions & 67 deletions src/expand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -189,21 +189,8 @@ impl Expand for [u8] {
*dest = source.clone();
}

macro_rules! next {
() => {
match parse(input) {
Ok((rest, item)) => {
input = rest;
item
}

Err(_) => return Err(error::Expand::Invalid.into()),
}
};
}

'main: while !input.is_empty() {
match next!() {
while !input.is_empty() {
match next_item(&mut input)? {
Item::Conditional(Conditional::If) => {
conditional = true;
}
Expand All @@ -216,24 +203,21 @@ impl Expand for [u8] {
Some(Parameter::Number(0)) => {
let mut level = 0;

while !input.is_empty() {
match next!() {
Item::Conditional(Conditional::End)
| Item::Conditional(Conditional::Else)
loop {
if input.is_empty() {
return Err(error::Expand::Invalid.into());
}
match next_item(&mut input)? {
Item::Conditional(Conditional::End | Conditional::Else)
if level == 0 =>
{
continue 'main
break
}

Item::Conditional(Conditional::If) => level += 1,

Item::Conditional(Conditional::End) => level -= 1,

_ => (),
}
}

return Err(error::Expand::Invalid.into());
}

Some(_) => (),
Expand All @@ -244,19 +228,17 @@ impl Expand for [u8] {
Item::Conditional(Conditional::Else) if conditional => {
let mut level = 0;

while !input.is_empty() {
match next!() {
Item::Conditional(Conditional::End) if level == 0 => continue 'main,

loop {
if input.is_empty() {
return Err(error::Expand::Invalid.into());
}
match next_item(&mut input)? {
Item::Conditional(Conditional::End) if level == 0 => break,
Item::Conditional(Conditional::If) => level += 1,

Item::Conditional(Conditional::End) => level -= 1,

_ => (),
}
}

return Err(error::Expand::Invalid.into());
}

Item::Conditional(..) => return Err(error::Expand::Invalid.into()),
Expand Down Expand Up @@ -325,36 +307,7 @@ impl Expand for [u8] {

Item::Operation(Operation::Binary(operation)) => match (stack.pop(), stack.pop()) {
(Some(Parameter::Number(y)), Some(Parameter::Number(x))) => {
stack.push(Parameter::Number(match operation {
Binary::Add => x + y,
Binary::Subtract => x - y,
Binary::Multiply => x * y,
Binary::Divide => {
if y != 0 {
x / y
} else {
0
}
}
Binary::Remainder => {
if y != 0 {
x % y
} else {
0
}
}

Binary::AND => x & y,
Binary::OR => x | y,
Binary::XOR => x ^ y,

Binary::And => (x != 0 && y != 0) as i32,
Binary::Or => (x != 0 || y != 0) as i32,

Binary::Equal => (x == y) as i32,
Binary::Greater => (x > y) as i32,
Binary::Lesser => (x < y) as i32,
}))
stack.push(Parameter::Number(eval_binary(operation, x, y)))
}

(Some(_), Some(_)) => return Err(error::Expand::TypeMismatch.into()),
Expand All @@ -363,10 +316,9 @@ impl Expand for [u8] {
},

Item::Operation(Operation::Unary(operation)) => match stack.pop() {
Some(Parameter::Number(x)) => stack.push(Parameter::Number(match operation {
Unary::Not => (x != 0) as i32,
Unary::NOT => !x,
})),
Some(Parameter::Number(x)) => {
stack.push(Parameter::Number(eval_unary(operation, x)))
}

Some(_) => return Err(error::Expand::TypeMismatch.into()),

Expand Down Expand Up @@ -534,6 +486,57 @@ impl Expand for [u8] {
}
}

fn next_item<'input>(input: &mut &'input [u8]) -> error::Result<Item<'input>> {
Ok(match parse(input) {
Ok((rest, item)) => {
*input = rest;
item
}

Err(_) => return Err(error::Expand::Invalid.into()),
})
}

fn eval_binary(operation: Binary, x: i32, y: i32) -> i32 {
match operation {
Binary::Add => x + y,
Binary::Subtract => x - y,
Binary::Multiply => x * y,
Binary::Divide => {
if y != 0 {
x / y
} else {
0
}
}
Binary::Remainder => {
if y != 0 {
x % y
} else {
0
}
}

Binary::AND => x & y,
Binary::OR => x | y,
Binary::XOR => x ^ y,

Binary::And => (x != 0 && y != 0) as i32,
Binary::Or => (x != 0 || y != 0) as i32,

Binary::Equal => (x == y) as i32,
Binary::Greater => (x > y) as i32,
Binary::Lesser => (x < y) as i32,
}
}

fn eval_unary(operation: Unary, x: i32) -> i32 {
match operation {
Unary::Not => (x != 0) as i32,
Unary::NOT => !x,
}
}

#[cfg(test)]
mod test {
#[test]
Expand Down