Changes between Version 4 and Version 5 of PIL

Timestamp:

10/03/24 20:42:43 (20 months ago)

Author:

siegel

Comment:

--

PIL

@@ -47 +47 @@
 
 There are two kinds of functions in PIL:
-1. Imperative functions = "procedures"
-1. Logic functions
+1. Imperative functions = "procedures".  A procedure has a type of the form `R(T1,...,Tn)` where `R` is the return type and the Ti are the input types.
+1. Logic functions.  One of these has a type of the form `$fun<R,T1,...,Tn>`.
 
 === Procedures
 
-Like in C.  These can be nested.  Obviously they can have side-effects, be nondeterministic, and the behavior can depend on non-local state.  A procedure call `f(x1,...,xn)` is an expression that can be used anywhere an expression with side-effects is allowed.  Imperative procedures are not values and cannot be assigned to anything.  However, as in C, a pointer to a procedure is a first-class value that can be assigned, used as an argument, returned, etc.   There is a procedure type, exactly like C's function type, e.g.,
+Like in C.  These can be nested.  Obviously they can have side-effects, be nondeterministic, and the behavior can depend on non-local state.  A procedure call `f(x1,...,xn)` is an expression that can be used anywhere an expression with side-effects is allowed.  Imperative procedures are not values and cannot be assigned to anything.  However, as in C, a pointer to a procedure is a first-class value that can be assigned, used as an argument, returned, etc.   There is a procedure type, similar to C's function type, e.g.,
 {{{
        typedef int(int) i2i;
@@ -60 +60 @@
        typedef int(int)* i2ip;
 }}}
-defines the type "pointer to procedure from int to int".  As in C, a pointer to a procedure can be used in a procedure call.
+defines the type "pointer to procedure from int to int".  As in C, a pointer to a procedure can be used in a procedure call.  It is an error to call a procedure f when f is not in scope.  (This is similar to Gnu C.)   In other words, if the call takes place in dyscope d, then the definition of f must be in d's static scope, or in the parent of d's static scope, or its parent, etc.
 
 A procedure definition can be templated:
@@ -70 +70 @@
 === Logic functions
 
-Typically specified by a $lambda expression. These are first-class objects in PIL: they can be assigned to variables, passed as an argument in a function call (including a procedure call), and can be returned by a function.  Each has a type of the form `$fun<U,T1,...,Tn>` (functions from `T1` x ... x `Tn` to `U`).  They are side-effect-free.  An application of a logic function `f(x1,...,xn)` is an expression that can be used anywhere an expression is allowed.  A logic function is not necessarily pure, i.e., the value of an application may depend on any part of the state, not just the arguments.
+Typically specified by a $lambda expression. These are first-class objects in PIL: one can be assigned to a variable, passed as an argument in a function call (including a procedure call), and can be returned by a function.  Each has a type of the form `$fun<U,T1,...,Tn>` (functions from `T1` x ... x `Tn` to `U`).  They are side-effect-free.  An application of a logic function `f(x1,...,xn)` is a side-effect-free expression that can be used anywhere an expression is allowed.  A logic function is not necessarily pure, i.e., the value of an application may depend on any part of the state, not just the arguments.
   
 === Lambda expressions