Lard Version 3 Release Notes

Upgrading from version 2

• Change your environment variables to point to the version 3 binaries and libraries. Just replace v2 with v3. Also, change your LCD_OPTS variable as indicated below under "Split library".

• Recompile all existing programs as the bcode intermediate format has changed slightly.

Changes since version 2

• Improved infix parser.

  An improved, though still not perfect, parser for infix expressions has been implemented. This substantially reduces the number of brackets needed. The remaining problem is with operators that have both unary and binary meanings including -, !, ? and =. These expressions may still need more brackets than would otherwise be necessary.

• Records.

  A proper implementation of records now exists.

• Overloading.

  A new class, overloaded, has been added. If an identifier is declared with this class then subsequently multiple declarations of that identifier are allowed. Uses of the identifier are class-checked with each declaration in turn, starting with the most recently declared and working backwards, until a matching declaration is found.

  A set of overloaded print functions has been added to the io library and the array indexing function _[_] is now overloaded on val and var parameters.

• Varargs functions.

  A new class, varargs, has been added. All instances of identifiers declared with this class are replaced by identifiers with the number of arguments appended, for example if the declaration foo:varargs is used, foo(a,b,c) is replaced by foo3(a,b,c). It is up to the user to declare foo3 in the usual way.

  A varargs print function has been added to the io library.

• Automatic val to expr and var to expr conversion.

  The compiler now automatically inserts calls to mkexpr so that when an expr parameter is required but a val or var expression is provided the necessary conversion takes place.

• Automatic class transformation for body expressions.

  The compiler will now add eval(), read() and mkexpr() as necessary to make the definition of a declaration match its class.

• Negative Literals.

  The way in which negative literals are parsed has been changed. This means that expressions such as (a-1), which used to cause problems, are now OK.

• Comments may now be nested.

• Bitwise and, or, xor, not and shifts.

• Vector constructor functions.

  A set of functions of the form [_:_:_:_] has been provided to construct vectors from their components.

• Split library.

  For ease of maintainance the library has been split up into several separate files. This means that the setting of the LCD_OPTS environment variable has to be changed to something like the following:

  -L/home/amuserv7/users/endecotp/lard/v3/lib -score -sops -stypes -splump -sctrl -lio -lchan -ltime

• rand improved.

  The random number function is now more random on the Sun, and always returns zero if passed zero as its argument.

• Optimiser debugged.

• Process viewer blobs debugged.

Still To Do

• Improved scheduler.
• Really good infix parser.
• String freeing mechanism.
• "Tables"
• Better implementation of libraries.

Known Bugs

• There can be class checking problems when using an expression in the class of a declaration, for example v:var(int^(a+1)). The problem hasn't been thoroughly investigated, but is seems that it can be made to go away using an explicit eval, for example v:var(int^(eval(a+1))).

• If a recursive function's return type depends on its parameters (explicit or implicit), things will go wrong. For example, compiling the following program fails to terminate:

  (foo(T:type):expr(T)=foo(T)).null