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Use Boole's rule to calculate integrate

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BenderBlog "SuperBart" Rodriguez 2024-07-12 14:27:56 +08:00 committed by GitHub
parent bcc0f947f9
commit 33f4f65e82
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1 changed files with 11 additions and 10 deletions
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21
kalk/src/numerical.rs
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@ -79,11 +79,11 @@ pub fn integrate(
expr: &Expr, expr: &Expr,
integration_variable: &str, integration_variable: &str,
) -> Result<KalkValue, KalkError> { ) -> Result<KalkValue, KalkError> {
Ok(simpsons_rule(context, a, b, expr, integration_variable)?.round_if_needed()) Ok(boole_rule(context, a, b, expr, integration_variable)?.round_if_needed())
} }
/// Composite Simpson's 3/8 rule /// Composite Boole's rule
fn simpsons_rule( fn boole_rule(
context: &mut interpreter::Context, context: &mut interpreter::Context,
a_expr: &Expr, a_expr: &Expr,
b_expr: &Expr, b_expr: &Expr,
@ -96,8 +96,8 @@ fn simpsons_rule(
.symbol_table .symbol_table
.get_and_remove_var(integration_variable); .get_and_remove_var(integration_variable);
const N: i32 = 900; const N: i32 = 1200;
let a = interpreter::eval_expr(context, a_expr, None)?; let a: KalkValue = interpreter::eval_expr(context, a_expr, None)?;
let b = interpreter::eval_expr(context, b_expr, None)?; let b = interpreter::eval_expr(context, b_expr, None)?;
let h = (b.sub_without_unit(&a))?.div_without_unit(&KalkValue::from(N))?; let h = (b.sub_without_unit(&a))?.div_without_unit(&KalkValue::from(N))?;
for i in 0..=N { for i in 0..=N {
@ -110,9 +110,10 @@ fn simpsons_rule(
)); ));
let factor = KalkValue::from(match i { let factor = KalkValue::from(match i {
0 | N => 1, 0 | N => 7,
_ if i % 3 == 0 => 2, _ if i % 4 == 0 => 14,
_ => 3, _ if (i - 2) % 4 == 0 => 12,
_ => 32,
} as f64); } as f64);
// factor * f(x_n) // factor * f(x_n)
@ -135,8 +136,8 @@ fn simpsons_rule(
let (h_real, h_imaginary, h_unit) = as_number_or_zero!(h); let (h_real, h_imaginary, h_unit) = as_number_or_zero!(h);
result.mul_without_unit(&KalkValue::Number( result.mul_without_unit(&KalkValue::Number(
3f64 / 8f64 * h_real, 4f64 / 90f64 * h_real,
3f64 / 8f64 * h_imaginary, 4f64 / 90f64 * h_imaginary,
h_unit, h_unit,
)) ))
} }