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Post Challenge

Comments on Evaluate a single variable polynomial equation

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Evaluate a single variable polynomial equation

+13
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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;
}
code-golf math
posted over 3 years ago
CC0
2y ago by user‭
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moony‭
554 reputation 10 6 68 43
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2 comment threads

Quadratic equation (1 comment)
General comments (2 comments)
Post
+0
−0

Python 3, 167 127 118 117 94 63 bytes

def f(a,b):
	y=0
	for z in range(len(a)):y+=a[z]*b**z
	print(y)

Try it online!

Close gap to @user's lambda answer!

Golfed 40 bytes thanks to @user's advice. Golfed another 9 bytes thanks to @user's advice.

posted over 2 years ago
2y ago
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General Sebast1an‭
1206 reputation 53 97 128 328
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1 comment thread

Several golfing opportunities (3 comments)
Several golfing opportunities
user‭ wrote over 2 years ago
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You can use 1 instead of True, use n+=[a] instead of n.append(a), drop the both the continues, and use for a in n: and then use a instead of n[i]. However, it'd be better to just use one loop instead of filling up an array and then iterating over it again. Even better would be a recursive lambda taking an array as input, although I understand if that approach isn't to your liking.

General Sebast1an‭ wrote over 2 years ago
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user‭ True, lambdas aren't really my thing, but thanks for the golfing ideas!

user‭ wrote over 2 years ago
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You can use an else instead of the continue, and you might want a slightly different input format to avoid the try/except stuff. However, I'd recommend taking a look at the other answers - you don't need z at all if you multiply by x each time and add the next coefficient (you'll have to take the highest degree first, then the lower ones).