Definition df-ceil 13756

Description: The ceiling (least integer greater than or equal to) function. Defined in ISO 80000-2:2009(E) operation 2-9.18 and the "NIST Digital Library of Mathematical Functions" , front introduction, "Common Notations and Definitions" section at http://dlmf.nist.gov/front/introduction#Sx4. See ceilval 13801 for its value, ceilge 13808 and ceilm1lt 13811 for its basic properties, and ceilcl 13805 for its closure. For example, (⌈‘(3 / 2)) = 2 while (⌈‘-(3 / 2)) = -1 (ex-ceil 30173).

The symbol ⌈ is inspired by the gamma shaped left bracket of the usual notation. (Contributed by David A. Wheeler, 19-May-2015.)

Assertion

Ref	Expression
df-ceil	⊢ ⌈ = (𝑥 ∈ ℝ ↦ -(⌊‘-𝑥))

Detailed syntax breakdown of Definition df-ceil

Step	Hyp	Ref	Expression
1		cceil 13754	. 2 class ⌈
2		vx	. . 3 setvar 𝑥
3		cr 11106	. . 3 class ℝ
4	2	cv 1532	. . . . . 6 class 𝑥
5	4	cneg 11443	. . . . 5 class -𝑥
6		cfl 13753	. . . . 5 class ⌊
7	5, 6	cfv 6534	. . . 4 class (⌊‘-𝑥)
8	7	cneg 11443	. . 3 class -(⌊‘-𝑥)
9	2, 3, 8	cmpt 5222	. 2 class (𝑥 ∈ ℝ ↦ -(⌊‘-𝑥))
10	1, 9	wceq 1533	1 wff ⌈ = (𝑥 ∈ ℝ ↦ -(⌊‘-𝑥))

This definition is referenced by:  ceilval  13801  dfceil2  13802