CTRex: Difference between revisions
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Labels (such as x,y and z) in CTRex are type level symbols (i.e. type level strings). We can point to a label by using the label type: | Labels (such as x,y and z) in CTRex are type level symbols (i.e. type level strings). We can point to a label by using the label type: | ||
< | <haskell>data Label (s :: Symbol) = Label</haskell> | ||
For example, we can declare shorthands for pointing at the type level symbol "x", "y" and "z" as follows. | For example, we can declare shorthands for pointing at the type level symbol "x", "y" and "z" as follows. | ||
< | <haskell> x = Label :: Label "x" | ||
y = Label :: Label "y" | |||
z = Label :: Label "z" </haskell> | |||
Revision as of 16:13, 4 December 2013
Introduction
This page will describe the design, usage and motivation for CTRex.
CTRex is a library for Haskell which implements extensible records using closed type families and type literals. It does not use overlapping instances.
What are extensible records?
A record is just a collection of label-value pairs. For example:
{ x = 0 , y = "bla", z = False }
Labels (such as x,y and z) in CTRex are type level symbols (i.e. type level strings). We can point to a label by using the label type:
data Label (s :: Symbol) = LabelFor example, we can declare shorthands for pointing at the type level symbol "x", "y" and "z" as follows.
x = Label :: Label "x"
y = Label :: Label "y"
z = Label :: Label "z"