Re: PCODE Interpereters 101

Dynamic links are, I believe necessary for languages where nested
declarations occur and up-level access is allowed. An example that is
tough (read: I think impossible) to execute properly without displays
is:


begin
string procedure foo( integer depth, string arg, string procedure
takeNote(string) )
{
string procedure parenthesized( string inArg )
{
return "(" & depth & ": " arg & " :" & inArg & ")";
}


  return (if 0 = depth then takeNote( arg )
eif 2 = depth then foo( depth-1, "<" & arg & ">", parenthesized )
else foo( depth-1, "[" & arg & "]", parenthesized )
}
string procedure braces( string inArg ) { return "{" & arg & "}"; }


foo( 4, "x", braces );
end




= foo(3, [x], braces)
= foo(2, [[x]], braces)
= foo(1, <[[x]]>, paren'2)
= foo(0, [<[[x]]>], paren'2)
= (2: [<[[x]]>], [[x]])




Where this comes up:
1) implementing an interpreter with stack allocation via recursive calls
to the interpreter.
2) implementing unification.


-Scott David Daniels
Scott.Daniels@Acm.Org

Return to the comp.compilers page.
Search the comp.compilers archives again.