Dick Grune

A view of coroutines

The coroutine mechanism is explained as a simplified implementation of a special case in parallel processing.

A programmer-friendly LL(1) parser generator

LL(1) grammars have the conceptual and practical advantage that they allow the compiler writer to view the grammar as a program; this allows a more natural positioning of semantic actions and a simple attribute mechanism. Resulting parsers can be constructed that achieve fully automatic error‐recovery, which allows the compiler writer to ignore totally the issue of syntax errors. Measurement shows that such parsers can be reasonably efficient.

Some statistics on ALGOL 68 programs

An attempt is made to assess some static and dynamic properties of ALGOL 68 programs, which are useful for optimization decisions. The results indicate that slicing and assignation are the most important candidates for optimization, and that optimization efforts need to be directed to the simple cases only.

How to produce all sentences from a two-level grammar

Abstract Two-level grammars are very readable formalisms for generating Chomsky Type 0 languages. Teaching and understanding them is greatly aided by the presence of a sentence generator. This paper shows how a usable sentence generator can be constructed. A working program is available from the author.

Towards the design of a super-language of ALGOL 68 for the Standard Prelude (Excerpt)

The problems concerning SIZETY definitions in an Unabridged Machine-Independent Standard Prelude for ALGOL 68 are examined and tentative solutions are given.

Two-level grammars are more expressive than Type 0 grammars: or are they?

Under some simple conditions, two-level grammars can generate languages with unbounded numbers of terminal symbols; Type 0 grammars cannot.

How to compare the incomparable

Abstract A technique for deciding between two processes, one with cost (x A , y A ) and the second with cost (x B , y B ), where x A > x B and y A B and no further information is available, is derived using dimension- and gauge-theory like arguments. The technique can be summarized as: If you cannot add them, multiply them.

Tokens to Syntax Tree — Syntax Analysis

There are two ways of doing parsing: top-down and bottom-up. For top-down parsers, one has the choice of writing them by hand or having them generated automatically, but bottom-up parsers can only be generated. In all three cases, the syntax structure to be recognized is specified using a context-free grammar; grammars were discussed in Section 1.8. Sections 3.2 and 3.5.10 detail considerations concerning error detection and error recovery in syntax analysis.

Generic packages in C

The structuring achieved by generic packages in Ada can be cheaply emulated in C by judicious use of the preprocessor. Two files are required for the generic package: the specification and the body. Two more files are used in the instantiation: one holding the instantiation parameters and one with auxiliary code. Instantiation results in normal C header and object files (*.h and *.o). Dependency control can be delegated to the make progam.

Detecting useless transitions in pushdown automata

Pushdown automata may contain transitions that are never used in any accepting run of the automaton. We present an algorithm for detecting such useless transitions. A finite automaton that captures the possible stack content during runs of the pushdown automaton, is first constructed in a forward procedure to determine which transitions are reachable, and then employed in a backward procedure to determine which of these transitions can lead to a final state. An implementation of the algorithm is shown to exhibit a favorable performance.