Shortest Floor Function

Question

Your task is to implement a floor function in as few bytes as possible.

A floor function is a function that takes a real number and returns the largest integer less than or equal to the input.

Your program should support both positive and negative inputs. Since it is provably impossible to support all real numbers you need only support a reasonable subset of them. This subset should include positive numbers, negative numbers and of course numbers that are not integers. Such number systems include fixed-point numbers, floating point numbers and strings.

Your code may be a complete program or function.

This is code-golf so answers will be scored in bytes with less bytes being a better score.

Answer 1

Mouse-2002, 13 bytes

Second place, ahh! (And this is a full program, not a function definition)

?&DUP &FRAC -

Take the fractional bit of the input and subtract it from the input.

Answer 2

Perl 5, 22 bytes

s/\..+//&&$_<0?$_--:$_

This is larger than my first answer, which merely truncated the number - so, for negative numbers, it wasn't correct. This was due to a misunderstanding on my part of what a floor function does.

Answer 3

RProgN, 1 byte

_

A builtin, thanks to the new challenge spec.

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Answer 4

AArch64 machine language (Linux), 8 bytes

0: 1e700000 fcvtms w0, d0
4: d65f03c0 ret

To try it out, compile and run the following C program

#include<stdio.h>
#include<math.h>
int f(double x){return floor(x);}
const char g[]="\x00\x00\x70\x1e\xc0\x03\x5f\xd6";

int main(){
  for( double d = -1.5; d < 1.5; d+=.2 ) {
    printf( "%f %d %d\n", d, f(d), ((int(*)(double))g)(d) );
  }
}

Answer 5

Wren, 16 bytes

Exactly ported from the PARI/GP answer.

Fn.new{|x|x-x%1}

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Wren, 26 bytes

Ported from the Keg answer.

Fn.new{|x|x.split(".")[0]}

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Answer 6

Keg, 6 5 4 bytes

:1%-

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^{Look ma, no unicode!}

A port of the RProgN2 answer

Answer 7

Python, 13

If the OP wants all functions to be non-anonymous, add f= to the front of each for two additional characters.

lambda x:x//1

Since x%1 returns the amount following the decimal point, this is pretty short (14):

lambda x:x-x%1

The shortest using string casting I could come up with (40):

lambda x:int(`x`.split('.')[0])+cmp(x,0)

Answer 8

Jelly, 1 byte

Ḟ

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or a non-builtin answer

%1_@

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How the second one works

%1_@ - Main link. Takes n on the left
%1   - Fractional part of n
  _@ - n - frac(n)

Answer 9

Python 3, 15 bytes

f=lambda n:n//1

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Answer 10

Pyth, 3 bytes

/Q1

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Answer 11

Lua, 27 25 18 15 bytes

print(...//1|0)

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Explanation

... variable-argument operator, returns the remaining arguments passed to the current function (top-level code block with all the program arguments in this case).

//1 floor divides by 1.

|0 bitwise OR, we use this to convert to an int.

Answer 12

MMIX, 8 bytes (2 instrs)

05000300 F8010000

Disassembly

    FIX $0,ROUND_DOWN,$0
    POP 1,0

MMIX has a builtin instruction for this. You can specify the rounding mode if you like, but you can use the default. (Options are towards 0, towards \$-\infty\$, towards \$\infty\$, or to nearest half to even.)

Honestly, I'd advise using a FIX directly, as opposed to calling.

Answer 13

ARBLE, 4 bytes

n//1

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Outputs with a leading .0. If this is forbidden, then...

ARBLE, 5 bytes

floor

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Answer 14

Thunno 2, 2 bytes

1÷

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Floor divide by one.

Funnily enough, Thunno 2 doesn't have a proper floor built-in. For positive numbers, you can use N (truncate), but that doesn't work for negative numbers.