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Functional Mini Component Pascal (FMCP) is the simplest of the MCP formalisations.
It forms the basis of the subsequent MCP versions and introduces a number of important
concepts that are extended and developed in the more complex languages. FMCP can be
seen as a 'minimal functional core' of Component Pascal.
FMCP is heavily influenced by Featherweight Java. Many of the conventions and shorthand
used in Featherweight Java -- such as the use of a fixed, globally-accessible class
table -- are adapted for in the FMCP type rules. However, as well as adapting the
definitions and type rules from Featherweight Java, we have also decided to model
certain aspects of Component Pascal that give the language its unique 'flavour' -- such
as the record extensibility modifier and the restriction on recursive value types.
Like Featherweight Java and Baby IL with Generics, FMCP is intended to be both a subset
of its parent language and purely functional. However, the lack of a 'new record value'
construct in Component Pascal means that FMCP is not quite a `pure' subset of Component
Pascal. For example, Java allows anonymous object creation expressions of the form "new
Object()", whereas there is no equivalent expression in Component Pascal. Therefore in
FMCP we add a "NEW R(...)" expression in order to ensure that the language is purely
functional.
Language features
FMCP supports the following features:
- Record type declarations;
- Record subtyping;
- INTEGER and BOOLEAN primitive types;
- Methods bounds to IN receiver types;
- Record field projection; and
- A "NEW R(...)" record instantiation expression.
As well as the NEW R(...) expression, there are a few other additions and simplifications
of Component Pascal language features. Since FMCP does not support record pointer types,
the receiver type of methods is always an IN record value type. This is a simplification
of the Component Pascal language requirement that a receiver type may be 'a VAR or IN of
record type T or a value parameter of type POINTER TO T (where T is a record type)' (from
the CP language report). Also, for the sake of simplicity, the receiver is always bound
to the variable "this".
The Component Pascal requirement that "the result type of a procedure can be neither a
record nor an array" is also removed - in FMCP, the return type of a method can be a
record value type.
We do not consider casting in FMCP, as the Component Pascal does not possess a Java or
C#-style cast expression (for example, "(Bar)new Foo()"), and attempting to adapt the
Component Pascal WITH construct for a functional language would be somewhat inelegant.
Casts are considered in the next MCP language, Imperative MCP.
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