Modules

Cayenne modules are simply named expressions that live in a global name space. Module names are distiguished by having a $ in the name. The module name space could be viewed a hierarchical with $ as the name separator (like UNIX path names use /).

A module definition looks like a simple definition except that it is preceeded by the keyword module.

module ::= module [concrete] modid :: type = expr ;

The type is not necessary and it can be left out.

module ::= module [concrete] modid = expr ;

The concrete modifier plays the same role here as for records, i.e. you can make the value of a module know instead of just its type.

Example

Some sample modules:

module foo$bar = 42;

module foo$baz =
open System$Int use Int, (+) in
struct {
inc :: Int -> Int;
inc x = x+1;
dec :: Int -> Int;
dec x = x-1;
};

#include

Most programs need values from the System modules. To get easy access to the entities defined in a module it is normally opened. This means that most modules will start out with a number of open constructs. To alleviate this problem there are some predefined set of texts that can be included in a module. These texts are inserted by simple text insertion with an #include.

`#include Prelude`

includes the following text

open System$String use * in
open System$List use * in
open System$Bool use  * in
open System$Char use * in
open System$Int use  * in
open System$Error use * in
open System$IO use * in
open System$Tuples use * in
open System$HO use * in

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Lennart Augustsson

Last modified: Mon Aug 31 01:39:59 CEST 1998