U+21F8 Rightwards Arrow with Vertical Stroke
U+21F8 was added in Unicode version 3.2 in 2002. It belongs to the block
This character is a Math Symbol and is commonly used, that is, in no specific script. The character is also known as z notation partial function.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+21F8 forms with similar adjacent characters prevents a line break inside it.
The Wikipedia has the following information about this codepoint:
In mathematics, a partial function f from a set X to a set Y is a function from a subset S of X (possibly the whole X itself) to Y. The subset S, that is, the domain of f viewed as a function, is called the domain of definition or natural domain of f. If S equals X, that is, if f is defined on every element in X, then f is said to be a total function.
More technically, a partial function is a binary relation over two sets that associates every element of the first set to at most one element of the second set; it is thus a univalent relation. It generalizes the concept of a (total) function by not requiring every element of the first set to be associated to an element of the second set.
A partial function is often used when its exact domain of definition is not known or difficult to specify. This is the case in calculus, where, for example, the quotient of two functions is a partial function whose domain of definition cannot contain the zeros of the denominator. For this reason, in calculus, and more generally in mathematical analysis, a partial function is generally called simply a function. In computability theory, a general recursive function is a partial function from the integers to the integers; no algorithm can exist for deciding whether an arbitrary such function is in fact total.
When arrow notation is used for functions, a partial function $f$ from $X$ to $Y$ is sometimes written as $f:X\rightharpoonup Y,$ $f:X\nrightarrow Y,$ or $f:X\hookrightarrow Y.$ However, there is no general convention, and the latter notation is more commonly used for inclusion maps or embeddings.
Specifically, for a partial function $f:X\rightharpoonup Y,$ and any $x\in X,$ one has either:
 $f\left(x\right)=y\in Y$ (it is a single element in Y), or
 $f\left(x\right)$ is undefined.
For example, if $f$ is the square root function restricted to the integers
 $f:Z\to N,$ defined by:
 $f\left(n\right)=m$ if, and only if, ${m}^{2}=n,$ $m\in N,n\in Z,$
then $f\left(n\right)$ is only defined if $n$ is a perfect square (that is, $0,1,4,9,16,\dots $). So $f\left(25\right)=5$ but $f\left(26\right)$ is undefined.
Representations
System  Representation 

Nº  8696 
UTF8  E2 87 B8 
UTF16  21 F8 
UTF32  00 00 21 F8 
URLQuoted  %E2%87%B8 
HTML hex reference  ⇸ 
Wrong windows1252 Mojibake  â‡¸ 
alias  z notation partial function 
Elsewhere
Complete Record
Property  Value 

3.2 (2002)  
RIGHTWARDS ARROW WITH VERTICAL STROKE  
—  
Arrows  
Math Symbol  
Common  
Other Neutral  
Not Reordered  
none  


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R 