N. Wirth. Programming with Modula-2. Springer-Verlag, Berlin, 1985.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....system developers of the late 70ies. Well known software engineering concepts like abstract data types [29] and programming in the large [9] have been invented to overcome these problems. Later on, these concepts have lead to the development of modular programming languages like Modula 2 [40] and Ada [37] the development of software design languages like HOOD [30] or EMIL [4, 24] and finally to the development of module concepts for knowledge base representation languages like EPSILON [7] and PROTOS L [2] Rather recently, a number of graph grammar researchers joint their efforts ....

....was found. Instead, the operations have a boolean character themselves: they succeed if the tree is actually empty or the element has been found in the tree and fail if the tree is not empty or the element is not present. Note that the module concept presented so far is influenced by Modula 2 [40]. Andreas J. Winter and Andy Schurr 9 Consequently we have no means to ensure that a module s interface actually constitutes an abstract data or graph type. A module (interface) itself is no more than a collection of declared resources. It is the responsibility of its creator to provide suitable ....

N. Wirth. Programming with Modula-2. Springer-Verlag, Berlin, 1985.

....specifications grow any further. It is almost impossible to keep specifications in a consistent state, and reusing generic parts of one specification within another one is not at all supported. The first solution to overcome these limitations was to adapt a module concept like those of Modula 2 [19] or Ada [17] which allows to break large specifications into smaller portions and to perform data abstraction for graph rewriting specifications [18] This approach was strongly influenced by well known software engineering concepts like Abstract Data Types [10] and Programming in the Large ....

N. Wirth. Programming with Modula-2. Springer-Verlag, Berlin, 1985.

.... f oo bar buzz , the string should be interpreted as two separate, consecutive greaterthan tokens. Upon encountering the string , the lexical analyzer needs to consult the parser to check the context in which the string occurs. For a second example, note that, in Modula 2 [10], integers, such as 10 , real numbers, such as 10. and the range symbol . are all allowed tokens. For the string 10. 20 , the partitioning yields the three tokens 10. and 20 if the longest match rule is observed strictly. But a correct partitioning in this case should be the the ....

N. Wirth, Programming with Modula-2 (2nd corrected ed.), Springer-Verlag, New York (1983).

....problem. To solve the lookahead problem, we define the class of finite lookahead finite automata (FFAs) which consists of the deterministic FAs (DFAs) that look ahead at most a finite number of symbols. Some languages may require infinite lookahead. For example, a hexadecimal number in Modula 2 [19] must end with the character H and a prefix of a hexadecimal number may look like an integer. This causes the problem of infinite lookahead. It is argued that real world scanners should utilize only finitelookahead FAs since it is difficult to handle buffers of potentially infinite size. ....

Wirth, N., Programming with Modula-2 (3rd corrected ed.), Springer-Verlag, New York (1985).

....automata combine suffix automata and cutoff states. Lexical analyzers based on generalized suffix automata can solve the (finite and infinite) look ahead problem without buffering and re scanning overhead. A practical application of generalized suffix automata is the lexical analyzers of Modula 2 [3], which may look ahead potentially infinite number of characters. Although generalized suffix automata, which are Moore machines, avoid the buffering and re scanning overhead, they still depend on auxiliary data structures to solve the look ahead problem. Generalized suffix automata can be further ....

.... 6 string, the scanner is determined to look for yet another quotation mark; it will never backtrack across the second quotation mark in the two consecutive quotation marks. Lexical analyzers for practical programming languages usually look ahead 2 characters. An exception is that of Modula 2 [3], which looks ahead potentially infinite number of characters. In Modula 2, a hexa decimal number consists of digits and the characters A through F and ends with an H . If there is no H at the end, the scanner must back up to the first occurrence of one of A through F . For instance, ....

N. Wirth, Programming with Modula-2 (3rd corrected ed.), Springer-Verlag, New York (1985).

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC