A CIL Tutorial - Department of Computer Science - ETH Zürich

Chapter 7
Type Qualiers
Over the next three chapters, we'll explore how to make changes to C's type-system. This will be
achieved by adding type-qualiers to C's types, and by performing some extra type-checking. In
this section, we'll write a very basic type-checker for types that may be qualied by one or more
of the following colors: red, green, or blue. In the exercises, you'll nd suggestions about how to
complete it. In the next section, we'll look at interpreting dependent type qualiers. Finally, in
Chapter 9, we'll see how to do some basic type qualier inference.
7.1 tut7.ml
In tut7.ml, rst we'll write functions to extract qualiers from types. Then, we'll perform our
additional type-checking.
7.1.1 Qualier Types
We'll dene some OCaml types representing the C type qualiers. Then, from C types, we'll extract
a possibly empty list of the qualiers.
type color = Red | Blue | Green
We'll set up some global constants for the string representation of the qualiers, and use them
everywhere instead of the strings, in case we want to change them later on.
let redStr = "red"
let blueStr = "blue"
let greenStr = "green"
Putting the strings in a list will help a bit later on.
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