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Scripts

In Miranda the script is the persistent entity that is saved from session to session (i.e. it plays the role of what is called a program in conventional languages). Associated with a Miranda session at any given time is a single current script, identified by a UNIX pathname ending in .m.

A script is a collection of declarations, establishing an environment in which you wish to evaluate expressions. The order of the declarations in a script is not significant - for example there is no requirement that an identifier be defined before it is used.

An identifier may not have more than one top-level binding in a given script.

Here are the kinds of declaration that can occur in a script:

1) a definition (of a function, data structure etc. - see manual entry definitions for more details). Example fac n = product[1..n]

2) a specification of the type of one or more identifiers, of the form var-list ::

Example

    fac :: num->num

See 'Basic type structure' for an account of possible types. Note that these type specifications are normally optional, since the compiler is able to deduce them from the definitions of the corresponding identifiers. It is however possible to introduce an identifier by means of a type specification only, without giving it a defining equation (such identifiers are said to be specified but not defined and are useful in program development). A special case of this is the introduction of an otherwise undefined typename - see separate manual entry on placeholder types.

3) the definition of a user defined type - these are of three kinds, synonyms, algebraic types, and abstract types (see separate manual entry on each).

4) a library directive (%export, %include or %free) these are used specify the interfaces between separately compiled scripts - see separate manual entry on the library mechanism.

There is a manual entry giving the formal syntax of Miranda scripts.

Note

A directory called ex' (meaningexamples) containing a collection of example scripts is supplied with the Miranda system, and will be found under themiralibdirectory (usually kept at /usr/lib/miralib - the Miranda session command/miralib` will tell you where it is on your system).

A convention which the Miranda system consistently understands in Miranda session commands, library directives etc. is that a pathname enclosed in , instead of "string_quotes" is relative to the miralib directory. In particular note that the Miranda session command

    /cd <ex>

will change your current directory to be "..../miralib/ex". You can then say, e.g.

    !ls

to see what's in there. In fact there is a README file, so a good thing to say next would be

    !vi README