Table of Contents
Prev Chapter 5. Patterns Next
5.8. As Pattern 5.9. Wildcard PatternChapter 6. Sites and Services 

5.9. Wildcard Pattern

The wildcard pattern matches any value and binds no variables.

5.9.1. Syntax

[36]WildcardPattern::= _  

5.9.2. Type

A wildcard pattern matches any type. The matching produces an empty typing context.

5.9.3. Examples

− Wildcard Assignments
{- Showcase various wildcard assignments -}

val (_,(_,x),_) = (0,(2,2),[5,5,5])
val [[_,y],[_,z]] = [[1,3],[2,4]]

[x, y, z]

{-
OUTPUT:
[2, 3, 4]
-}
− Implication by Fewer Cases
{-
  Defining logical implication by cases, 
  using wildcard to abbreviate the 'true' cases. 
-}

def implies(true, false) = false
def implies(_, _) = true

implies(true, true)

{-
OUTPUT:
true
-}

5.9.4. Related Links

Related Reference Topics

Related Tutorial Sections