EULER: A Generalization ALGOL, and its Formal Definition: Part I*
A method for defining programming languages is
developed which introduces a rigorous relationship 
between structure and meaning.  The structure of a
language is defined by a phrase structure syntax, 
the meaning in terms of the effects which the execution
of a sequence of interpretation rules exerts 
upon a fixed set of variables, called the Environment.
 There exists a one-to-one correspondence between 
syntactic rules and interpretation rules is determined by
the sequence of corresponding syntactic reductions 
which constitute a parse.  The individual interpretation
rules are explained in terms of an elementary 
an d obvious algorithmic notation.  A constructive
method for evaluating a text is provided, and for 
certain decidable classes of languages their unambiguity
is proved.  As an example, a generalization 
of ALGOL is described in full detail to demonstrate that
concepts like block-structure, procedures, parameters, 
etc. can be defined adequately and precisely by this method.
CACM January, 1966
Wirth, N.
Weber, H.
