Parse tree

The rule is parsed in a top-down fashion(l6) using a BNF driven parser according to the explicit grammar, a portion of which is shown in Figure 5. This is a fairly simple context free grammar, written in the BNF (Backus Normal Form) style.(17) A condensed version of the parse tree for the sample rule is shown in Figure 6. Semantic analysis checks for ... 

Figure 6. Simplified parse tree of the ALPHA-TO-SC rule.

The set of internal nodes used in the parse trees is known as the function set F, where F = /i,/2, All functions have an arity (the number of arguments) greater than 1. The set of terminal (leaf) nodes in the parse tree is, predictably,... 

Fig. 13 A simple parse tree for the expression 4x + 17x2 - 11 cosy...

Architecture-altering operations are used to extend the scope of GP by providing a means by which branches and arguments within the parse trees may be created or deleted. Permutation, which swaps characters in a tree, and editing, which involves the optimisation of long expressions, are also commonly used. 

Figure 2b. Parse tree of (CH,),C=CHCH OH, a representative terpenoid...

A simple parse tree is illustrated in Fig. 7. The nodes of a tree contain functions, such as + or —, while the leaves contain the arguments to that function. Notice that, because all functions in a parse tree return a value, it is possible to pass the result of a function as the argument to another function. For example, the expression a -h b c would be represented as in Fig. 7. 

Parse trees also have a convenient linear representation, identical to that used in the language Lisp. For example, the left tree in Fig. 7 would be (4- 1 2), i.e., the function followed by its arguments, while the right tree in Fig. 7 would be described by (+ a ( b c)). Because of the close relationship between Lisp and parse trees and the... 

The following grammar demonstrates some aspects of writing a DCG in Prolog. It produces the complete parse tree of the sentence. It handles some form of number agreement. (A sentence like The boy kick the ball would be rejected.). Finally, it separates grammar rules from the dictionary. In this form it is easier to maintain the grammar ... 

This grammar allows one to parse the original sentence The boy kicked the ball, producing the following parse tree ... 

The analysis of an input string by an AGinterpretor jnoceeds in two biases. In the first, c ed syntax analysis, a context-free parser is used to construct a parse tree df the itqmt string, hi Ae second, called semantic analysis, the values df the attributes at the nodes of the parse tree are evaluated and the semantic conditions are tested. 

The main difierence between the two algorithms is their evaluation order. ASAP moves from the root of the ClX to the leaves Miiilc ALAP moves the ofiier way. This was reflected in the AGs presented in (Economakos, 1995). Since idl attributes were attached to the parse tree the givoi behavior, by examining the HIX syntax given in figure 1, one can easily see that ASAP required attribute instance dependencies with direction fr n the leaves of each subtree to its root and ALAP the opposite. In AG terminology, ASAP required synthesized attributes while ALAP required inherited ones. 

We can depict this derivation graphically, as a.derivation tree, sometimes called a parse tree. 

Linking values in the GDB (ISPS parse tree) and the Value Trace, and linking the behavioral and structural domains. 

Each task of the parse tree, with the leaves representing source tokens and vertices representing semantic units, is mapped into a graph incorporating both control flow and data flow, with vertices representing primitive operations. Lifetime analysis is used to represent the data flow in single-assignment form. 

A TOOL tree is an abstract syntax tree that resembles a parse tree with the difference that punctuation terminals in the grammar such as parentheses do not appear in the tree. Control constructs are not broken down into tests and jumps but are retained as trees. Figure 7-3 shows examples of TCOL trees. 

Now we can get a short definition of the notion syntax derivation, that is the base for the definition of the parse tree. 

Definition A parse tree of a statement ST is the K-ary tree that represents the syntax derivation S=(S1,.Sn) of ST. 

The parser analyses statement by statement and writes the interface data structures onto the parse tree file. 

---