Why pow(-1, 0) returns 1 instead of -1?

Question

As google suggests -1⁰=-1. And as I understand pow() function in javascript, python and C should return the same result. But it's not true. Why?

Python:

>>> pow(-1, 0)
1

Don't you see what's actually being calculated? In the little calculator area, Google is actually interpreting your input as `-(1 ^ 0)` — Ian, Aug 19 '13 at 18:02
Hey guys, that's basic math. At least learn how to use a calculator. — alk, Aug 19 '13 at 18:03
`Math.pow(-1, 0)` (JavaScript) and `pow(-1.0, 0)` (C) also return 1. — nderscore, Aug 19 '13 at 18:07
@GrijeshChauhan Zero to the zero is ambiguous: http://stackoverflow.com/a/17368335/1708801 — Shafik Yaghmour, Aug 19 '13 at 18:07

score 9 · Accepted Answer · answered Aug 19 '13 at 17:57

9

It's a precedence thing. Google thinks (-1)⁰ = 1, as does Python:

>>> (-1)**0
1

Any nonzero number raised by the exponent 0 is 1.

answered Aug 19 '13 at 17:57

John Kugelman

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@Dmitry: Because `pow(-1, 0) == (-1)**0`, not `-(1**0)`. – user2357112 Aug 19 '13 at 18:00
Thank you - it's an answer! :) – Dmitry Aug 19 '13 at 18:02

score 3 · Answer 2 · edited Aug 19 '13 at 18:19

3

You forgot the parenthesis!

-1 ^ 0 = -(1 ^ 0) = -(1) = -1

because power operator has higher precedence.

But:

(-1)^0 = 1

See on Google

edited Aug 19 '13 at 18:19

Grijesh Chauhan

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answered Aug 19 '13 at 17:58

julienc

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score 1 · Answer 3 · answered Aug 19 '13 at 17:59

1

Anything to the power of 0 will result to 1.

Remember BEDMASS. Your google example executes Brackets (1^0) which is 1, then you executed Multiplication, negating your expression in the brackets to -1.

answered Aug 19 '13 at 17:59

clamchoda

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score 1 · Answer 4 · edited Aug 19 '13 at 18:13

1

(-1⁰) is the same as saying (-1/-1) which is 1.

In division you substract the exponent of the denominator from the exponent of the numerator. For this rule to hold true all number elevated to the power of zero is 1. 5¹ / 5¹ = 5⁰ = 1

edited Aug 19 '13 at 18:13

Grijesh Chauhan

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answered Aug 19 '13 at 18:07

edi_allen

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Why not `1/1` ? I think you wants to say `(-1 ^ 0)` == `( -1 ^ (1 -1))` == `-1 ^1 * -1 ^ -1` == `-1/ -1` Then Nice answer! – Grijesh Chauhan Aug 19 '13 at 18:10
What I meant was that (-1^0) == **((-1^1) / (-1^1))**. Applying the rule of exponent to the second expresion give you -1^0 which is 1. Every number divided by itself equal 1 (except for zero). – edi_allen Aug 19 '13 at 18:53

Why pow(-1, 0) returns 1 instead of -1?

4 Answers4