Comments on Evaluate a single variable polynomial equation
Parent
Evaluate a single variable polynomial equation
Challenge
Given a list of n numbers and x, compute $a + bx^1 + cx^{2} + ... + zx^{n-1}$, where a is the first value in the list, b is the second, etc. n is at most 256 and at least 0. The input value(s) can be any 32-bit float
Input can be in any format of choice, as long as it is a list of numbers and x. (And this'll likely stay this way, even if input rules change over time)
Test inputs
[1.0], 182 -> 1
[1.0, 2.0], 4 -> 9
[2.5, 2.0], 0.5 -> 3.5
[1.0, 2.0, 3.0, 4.0], 1.5 -> 24.25
Example ungolfed program (Rust)
// dbg! is a logging function, prints the expression and it's output.
// Good for seeing what's happening
// Test setup
pub fn main() {
let inp: &[f32] = &[1.0, 2.0, 3.0, 4.0];
let x: f32 = 1.5;
dbg!(evaluate_polynomial(inp, x)); // take inputs, print result
}
// Actual challenge answer function
pub fn evaluate_polynomial(inp: &[f32], x: f32) -> f32 {
let mut accum: f32 = 0.0;
for (idx, val) in inp.iter().enumerate() {
// x.pow(idx) * val
accum += dbg!(x.powf(idx as f32) * val);
}
return accum;
}
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Post
Ruby, 50 bytes
def f(k,x)k.length>1?k[0]+f(k[1..-1],x)*x:k[-1]end
This uses the Horner's method recursively, because I think it'll be slightly shorter than using a loop or builtin array functions.
Also, this is my first post on this website ... er my first real attempt at golfing something in Ruby, so please feel free to suggest ways to shorten my solution.
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