Partial application

<p>In <a href="/facts/Computer_science/lN3pEyPz">computer science</a>, partial application (or partial function application) refers to the process of fixing a number of arguments of a function, producing another function of smaller <a href="/facts/Arity/zSVuwHvP">arity</a>.  Given a function 
  
    
      
        f
        :
        (
        X
        ×
        Y
        ×
        Z
        )
        →
        N
      
    
    {\displaystyle f\colon (X\times Y\times Z)\to N}
  
, we might fix (or 'bind') the first argument, producing a function of type 
  
    
      
        
          partial
        
        (
        f
        )
        :
        (
        Y
        ×
        Z
        )
        →
        N
      
    
    {\displaystyle {\text{partial}}(f)\colon (Y\times Z)\to N}
  
.  Evaluation of this function might be represented as 
  
    
      
        
          f
          
            partial
          
        
        (
        2
        ,
        3
        )
      
    
    {\displaystyle f_{\text{partial}}(2,3)}
  
.  Note that the result of partial function application in this case is a function that takes two arguments. Partial application is sometimes incorrectly called <a href="/facts/Currying/AmD3PP5B">currying</a>, which is a related, but distinct concept.
</p>

Partial application open-in-new

Partial application