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this grammar
 
Yoix supports a this keyword without officially providing classes, so the semantics do not duplicate what you may be familiar with from Java. In Yoix this is normally used in the body of a function, and in that case it refers to a compound object, like a Dictionary, that contains the definition of the function that is being executed, which we often call the "function's context". When a function is defined in a block this will be a Dictionary that references the local variables defined in that block. There are no restrictions on where this can be used, but if it is not in the body of a function then this and global will be synonyms.

The fact that a function can be used in an assignment statement or as the argument in another function call means the function's context can change, and those changes are always captured by this. In other words, the evaluation of this is a runtime event and the answer is dynamic and changes when a program "moves" a function around using assignment statements.
 
 Example:   The first program, 
import yoix.stdio.*;

int a = 1;
{
    int a = 10;
    {
        int a = 100;
        int b = -1;
        f() {
            int a = 1000;

            printf("       a=%d\n", a);
            printf("  this.a=%d\n", this.a);
            printf("global.a=%d\n\n", global.a);
            if (this.a++ == 102)
                printf("this=%O\n\n", this);
        }
        f();
        f();
        f();
    }
}
is a simple example that prints 
       a=1000
  this.a=100
global.a=1

       a=1000
  this.a=101
global.a=1

       a=1000
  this.a=102
global.a=1

this=Dictionary[3:0]
    a=103
    b=-1
   >f=f()
on standard output, which illustrates how this works when a function is defined in a block.

The next program 

import yoix.stdio.*;

String UNDEF = "<undef>";
String tree = "cedar";

Dictionary tester[0, ...] = {      // growable dictionary
    String tree = "oak";

    SetVariables(...) {
        String tree = "spruce";
        String type = "blue";

        printf("inside before tree: %s\n", this.tree);
        printf("inside before type: %s\n",
            defined("type", this) ? this.type : UNDEF);

        while(argv@sizeof > 2)
            this[ *++argv ] = *++argv;

        printf("inside after  tree: %s\n", this.tree);
        printf("inside after  type: %s\n",
            defined("type", this) ? this.type : UNDEF);
    }
};

printf("global before tree: %s\n", this.tree);
printf("global before type: %s\n",
       defined("type", this) ? this.type : UNDEF);
printf("tester before tree: %s\n", tester.tree);
printf("tester before type: %s\n",
       defined("type", tester) ? tester.type : UNDEF);

tester.SetVariables("tree", "maple", "type", "sugar");

printf("tester after  tree: %s\n", tester.tree);
printf("tester after  type: %s\n",
       defined("type", tester) ? tester.type : UNDEF);
printf("global after  tree: %s\n", this.tree);
printf("global after  type: %s\n",
       defined("type", this) ? this.type : UNDEF);
is a little more complicated and prints 
global before tree: cedar
global before type: <undef>
tester before tree: oak
tester before type: <undef>
inside before tree: oak
inside before type: <undef>
inside after  tree: maple
inside after  type: sugar
tester after  tree: maple
tester after  type: sugar
global after  tree: cedar
global after  type: <undef>
on standard output. Notice that the while-loop in SetVariables can create new entries in the tester dictionary, which is why we made it growable.
 
 See Also:   functions, global, reference

 

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