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Performance improved for sqrt, cbrt, factorial

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This commit is contained in:
Kasper 2019-12-28 00:37:40 +01:00
parent de99482c98
commit a0b7a7cdf5
1 changed files with 9 additions and 7 deletions
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16
src/evaluator.rs
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@ -28,18 +28,19 @@ pub fn evaluate(ast: &AstNode) -> Result<Answer, String> {
Ok(answer) Ok(answer)
} }
fn factorial(n: d128) -> d128 { fn factorial(n: d128, one: d128, two: d128) -> d128 {
if n < d128!(2) { if n < two {
d128!(1) one
} else { } else {
n * factorial(n - d128!(1)) n * factorial(n - one, one, two)
} }
} }
fn sqrt(input: d128) -> d128 { fn sqrt(input: d128) -> d128 {
let mut n = d128!(1); let mut n = d128!(1);
let half = d128!(0.5);
for _ in 0..10 { for _ in 0..10 {
n = (n + input/n) * d128!(0.5); n = (n + input/n) * half;
} }
return n return n
} }
@ -47,9 +48,10 @@ fn sqrt(input: d128) -> d128 {
fn cbrt(input: d128) -> d128 { fn cbrt(input: d128) -> d128 {
let mut n: d128 = input; let mut n: d128 = input;
// hope that 20 iterations makes it accurate enough // hope that 20 iterations makes it accurate enough
let three = d128!(3);
for _ in 0..20 { for _ in 0..20 {
let z2 = n*n; let z2 = n*n;
n = n - ((n*z2 - input) / (d128!(3)*z2)); n = n - ((n*z2 - input) / (three*z2));
} }
return n return n
} }
@ -190,7 +192,7 @@ fn evaluate_node(ast_node: &AstNode) -> Result<Answer, String> {
} else if child_answer.value > d128!(1000) { } else if child_answer.value > d128!(1000) {
Err("Cannot perform factorial of numbers above 1000".to_string()) Err("Cannot perform factorial of numbers above 1000".to_string())
} else { } else {
Ok(Answer::new(factorial(child_answer.value), child_answer.unit)) Ok(Answer::new(factorial(child_answer.value, d128!(1), d128!(2)), child_answer.unit))
} }
}, },
} }