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Fixed issue #1 on unit tests and eval function
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@mbartelsm
mbartelsm committed Oct 16, 2019
1 parent 0a2756d commit b72a7d5
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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ The objective of this project is to serve as a valuable learning experience in t
## To do

- [X] Implement evaluation
- [ ] Fix issue [#1](/../../issues/1)
- [X] Fix issue [#1](/../../issues/1)
- [ ] Implement parentheses parsing
- [ ] Implement basic algebraic operators
- [ ] Negative sign
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105 changes: 69 additions & 36 deletions src/main.rs
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Expand Up @@ -187,26 +187,25 @@ fn to_postfix(tokens: &mut Vec<Token>) -> Vec<Token> {
}

/// Recursively evaluates a vector holding tokens in postfix form, returns a Result
fn eval_postfix<'a>(expr: &mut Vec<Token>) -> Result<f64, &'a str> {
fn eval_postfix<'a>(mut expr: &mut Vec<Token>) -> Result<f64, &'a str> {

// If expression is empty, return error
// If next item is a number, return it
let op = match expr.pop().unwrap() {
Token::None => { return Err("Expected something, found nothing"); },
Token::Number(num) => { return Ok(num); },
w => w
let op = match expr.pop() {
Some(e) => match e {
Token::None => { return Err("Expected something, found nothing"); },
Token::Number(num) => { return Ok(num); },
w => w
}
None => { return Err("Expected something, found nothing"); }
};

let mut expr = expr.clone();

// Eval first sub-expression recursively
let a = match eval_postfix(&mut expr) {
Ok(n) => n,
Err(e) => { return Err(e); }
};

let mut expr = expr.clone();

// Eval second sub-expression recursively
let b = match eval_postfix(&mut expr) {
Ok(n) => n,
Expand All @@ -217,11 +216,13 @@ fn eval_postfix<'a>(expr: &mut Vec<Token>) -> Result<f64, &'a str> {
let ans = match op {
Token::TermOp('+') => a + b,
Token::TermOp('-') => a - b,
Token::TermOp(_) => { return Err("Invalid Token"); }
Token::ProdOp('*') => a * b,
Token::ProdOp('/') => {
if b == 0.0 { return Err("Undefined: Division by zero"); }
a / b
},
Token::ProdOp(_) => { return Err("Invalid Token"); }
_ => 0.0 // Compiler complained without this even though it's covered in the base case
};

Expand All @@ -238,6 +239,7 @@ fn main() {
},
};
let mut tokens = to_postfix(&mut tokens);
println!("{:?}", tokens);
let answer = eval_postfix(&mut tokens).unwrap();
println!("Answer is {}", answer);
}
Expand All @@ -258,51 +260,82 @@ mod unit_tests {
assert_eq!(Ok(0.0),eval_postfix(&mut expr));

// 1 * 1 = 1
// FIXME: Division and multiplication always yield 0.0
// let mut expr = vec![Token::Number(1.), Token::Number(1.), Token::TermOp('*')];
// assert_eq!(Ok(1.0),eval_postfix(&mut expr));
let mut expr = vec![Token::Number(1.), Token::Number(1.), Token::ProdOp('*')];
assert_eq!(Ok(1.0),eval_postfix(&mut expr));

// 2 * 1 = 1
// let mut expr = vec![Token::Number(2.), Token::Number(1.), Token::TermOp('*')];
// assert_eq!(Ok(1.0),eval_postfix(&mut expr));
// 2 * 1 = 2
let mut expr = vec![Token::Number(2.), Token::Number(1.), Token::ProdOp('*')];
assert_eq!(Ok(2.0),eval_postfix(&mut expr));

// 2 * 0 = 0
let mut expr = vec![Token::Number(2.), Token::Number(0.), Token::TermOp('*')];
let mut expr = vec![Token::Number(2.), Token::Number(0.), Token::ProdOp('*')];
assert_eq!(Ok(0.0),eval_postfix(&mut expr));

// 1 / 1 = 1
// let mut expr = vec![Token::Number(1.), Token::Number(1.), Token::TermOp('/')];
// assert_eq!(Ok(1.0),eval_postfix(&mut expr));
let mut expr = vec![Token::Number(1.), Token::Number(1.), Token::ProdOp('/')];
assert_eq!(Ok(1.0),eval_postfix(&mut expr));

// 2 / 2 = 1
// let mut expr = vec![Token::Number(2.), Token::Number(2.), Token::TermOp('/')];
// assert_eq!(Ok(1.0),eval_postfix(&mut expr));
let mut expr = vec![Token::Number(2.), Token::Number(2.), Token::ProdOp('/')];
assert_eq!(Ok(1.0),eval_postfix(&mut expr));

// 2 / 1 = 2
// let mut expr = vec![Token::Number(2.), Token::Number(1.), Token::TermOp('/')];
// assert_eq!(Ok(2.0),eval_postfix(&mut expr));
let mut expr = vec![Token::Number(1.), Token::Number(2.), Token::ProdOp('/')];
assert_eq!(Ok(2.0),eval_postfix(&mut expr));

// 2 / 0 = Err
// let mut expr = vec![Token::Number(2.), Token::Number(0.), Token::TermOp('/')];
// let ans = eval_postfix(&mut expr);
// assert_matches!(ans, Err(_));
let mut expr = vec![Token::Number(0.), Token::Number(2.), Token::ProdOp('/')];
let ans = eval_postfix(&mut expr);
assert_matches!(ans, Err(_));

// 1 * = Err
// TODO: Catch panic appropriately, Failing at None on unwrap
// let mut expr = vec![Token::Number(1.), Token::TermOp('*')];
// let ans = eval_postfix(&mut expr);
// assert_matches!(ans, Err(_));
let mut expr = vec![Token::Number(1.), Token::ProdOp('*')];
let ans = eval_postfix(&mut expr);
assert_matches!(ans, Err(_));

// 1 + 1 + 1 = 3
let mut expr = vec![Token::Number(1.), Token::Number(1.), Token::TermOp('+'), Token::Number(1.), Token::TermOp('+')];
assert_eq!(Ok(3.0),eval_postfix(&mut expr));

// 2 + 2 * 3 = 8
// let mut expr = vec![Token::Number(2.), Token::Number(3.), Token::TermOp('*'), Token::Number(2.), Token::TermOp('+')];
// assert_eq!(Ok(8.0),eval_postfix(&mut expr));

// 2 + 2 * 3 = 8, alternate postfix form
// let mut expr = vec![Token::Number(2.), Token::Number(2.), Token::Number(3.), Token::TermOp('*'), Token::TermOp('+')];
// assert_eq!(Ok(8.0),eval_postfix(&mut expr));
// Test forms
// 4 + 2 * 3 = 8
let mut expr = vec![
Token::Number(4.),
Token::Number(2.),
Token::Number(3.),
Token::ProdOp('*'),
Token::TermOp('+')
];
assert_eq!(Ok(10.0),eval_postfix(&mut expr));

// 4 + 2 * 3 = 8
let mut expr = vec![
Token::Number(4.),
Token::Number(3.),
Token::Number(2.),
Token::ProdOp('*'),
Token::TermOp('+')
];
assert_eq!(Ok(10.0),eval_postfix(&mut expr));

// 4 + 2 * 3 = 8
let mut expr = vec![
Token::Number(2.),
Token::Number(3.),
Token::ProdOp('*'),
Token::Number(4.),
Token::TermOp('+')
];
assert_eq!(Ok(10.0),eval_postfix(&mut expr));

// 4 + 2 * 3 = 8
let mut expr = vec![
Token::Number(3.),
Token::Number(2.),
Token::ProdOp('*'),
Token::Number(4.),
Token::TermOp('+')
];
assert_eq!(Ok(10.0),eval_postfix(&mut expr));
}
}

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