Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Challenges

Evaluate a single variable polynomial equation

+12
−0

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;
}
History
Why does this post require moderator attention?
You might want to add some details to your flag.
Why should this post be closed?

2 comment threads

Quadratic equation (1 comment)
General comments (2 comments)

20 answers

You are accessing this answer with a direct link, so it's being shown above all other answers regardless of its score. You can return to the normal view.

+4
−0

JavaScript (Node.js), 40 bytes

f=(a,b,c=1)=>a.reduce((d,e)=>d+e*(c*=b))

Try it online!

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+9
−0

APL (Dyalog Unicode), 11 3 1 byte

Try it online!

Anyone who can golf this further gets a cookie!

Function submission which takes reversed coefficients as right argument and $x$ as left argument.

-8 bytes from dzaima and rak1507(APL Orchard).

-2 bytes from Adám‭.

Uses a mixed base conversion.

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+5
−0

Japt -x, 6 5 bytes

Ë*VpE

Try it

Ë*VpE     :Implicit input of array U and float V
Ë         :Map each element D at 0-based index E
 *        :  Multiply D by
  VpE     :  V raised to the power of E
          :Implicit output of sum of resulting array
History
Why does this post require moderator attention?
You might want to add some details to your flag.

1 comment thread

General comments (2 comments)
+5
−0

Ruby, 50 bytes

def f(k,x)k.length>1?k[0]+f(k[1..-1],x)*x:k[-1]end

Try it online!

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.

History
Why does this post require moderator attention?
You might want to add some details to your flag.

1 comment thread

Tips (44 bytes) (1 comment)
+4
−0

Haskell, 20 bytes

f x=foldl((+).(x*))0

Try it online!

Takes input coefficients from highest degree to lowest.

21 bytes

x%(h:t)=h+x*x%t
x%_=0

Try it online!

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+4
−0

Japt, 12 bytes

ÊÆgX *VpXÃr+

Loops through the range of integers 0 to n-1, calculates each term, and sums.

Try it

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+4
−0

Raku, 19 bytes

(*Z*(*X**0..*)).sum

Try it online!

Is it concerning that my solution is over 30% asterisks?

Explanation

(             ).sum  # Get the sum of
 *Z*(        )       # The input list zip multiplied by
     *X**            # The second input to the power of
         0..*        # 0 to infinity

An alternate curried solution for 19 bytes is:

{*.reduce(*×$_+*)}

Try it online!

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+4
−0

Vyxal, 6, 5, 4 bytes

Źe*∑

Try it Online!

Takes input in the format coeffs, x

Explained

Źe*∑
Ź      # Generate range [0, len(coeffs))
 e     # Calculate x ** [0, len(coeffs) (vectorising)
  *    # Multiply the coefficients by the exponated x's. The lists are extended with 0s to be the same length
   ∑   # Sum that list and output
History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+4
−0

Ruby, 38 bytes

Simple map and sum over the coefficients. No TIO link, this uses numbered lambda parameters which require Ruby 2.7.

->l,x{l.each_with_index.sum{_1*x**_2}}
History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+3
−0

Jelly, 1 byte

Try it online!

Essentially just Razetime's APL answer, except in that vectorizes rather than carrying out mixed base conversion--irrelevant if, as is the case here, the provided base is scalar. Takes a reversed coefficient list on the left and $x$ on the right.

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+2
−0

JavaScript (Node.js), 33 bytes

a=>n=>a.reduce((o,x,y)=>o+x*n**y)

Try it online!

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+2
−0

Pyth, 10 bytes

s*R^H~hZhA

Try it online!


Alternate 10 byte solution:

s.e*b^eQkh

Try it online!

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+1
−0

Python 3, 46 bytes

lambda a,x:sum(c*x**i for i,c in enumerate(a))

Try it online!

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+1
−0

Python 3, 46 bytes

f=lambda p,x,a=0:p and f(p[1:],x,a*x+p[0])or a

Try it online!

Takes input reversed.

History
Why does this post require moderator attention?
You might want to add some details to your flag.

1 comment thread

General (1 comment)
+1
−0

Scala, 18 bytes

x=>_.:\(.0)(_+_*x)

Try it online!

Not too complicated. Takes the list of coefficients and folds from the right, multiplying the accumulator by x each time and adding the next coefficient. reduceRight would've worked instead of :\(0), but it's golfier, and I haven't used /: or :\ in a while.

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+1
−0

C++ (gcc), 61 bytes

float f(int n,float*p,float x){return n?*p+x*f(n-1,p+1,x):0;}

Try it online!

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+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.

History
Why does this post require moderator attention?
You might want to add some details to your flag.

1 comment thread

Several golfing opportunities (3 comments)
+0
−0

J, 2 bytes

p.

Try it online!

J likes inflections so it won't beat APL, but J is still a contender :).

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+0
−0

BQN, 13 bytes

{+´(𝕨⋆↕≠𝕩)×𝕩}

{           }  # fn
 +´            # sum reduce
   (𝕨⋆↕≠𝕩)     # x^i for each term
          ×𝕩   # times each coefficient

Try it

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

+0
−0

Ruby, 29 bytes

->l,x{a,*b=l;a ?a+x*f[b,x]:0}

Try it online

History
Why does this post require moderator attention?
You might want to add some details to your flag.

0 comment threads

Sign up to answer this question »