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META II
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META II
META II is a domain-specific programming language for writing compilers. It was created in 1963–1964 by Dewey Val Schorre at University of California, Los Angeles (UCLA). META II uses what Schorre called syntax equations. Its operation is simply explained as:
Each syntax equation is translated into a recursive subroutine which tests the input string for a particular phrase structure, and deletes it if found.
Meta II programs are compiled into an interpreted byte code language. VALGOL and SMALGOL compilers illustrating its capabilities were written in the META II language, VALGOL is a simple algebraic language designed for the purpose of illustrating META II. SMALGOL was a fairly large subset of ALGOL 60.
META II was first written in META I, a hand-compiled version of META II. The history is unclear as to whether META I was a full implementation of META II or a required subset of the META II language required to compile the full META II compiler.
In its documentation, META II is described as resembling Backus–Naur form (BNF), which today is explained as a production grammar. META II is an analytical grammar. In the TREE-META document, these languages were described as reductive grammars.
For example, in BNF, an arithmetic expression may be defined as:
BNF rules are today production rules describing how constituent parts may be assembled to form only valid language constructs. A parser does the opposite taking language constructs apart. META II is a stack-based functional parser programming language that includes output directive. In META II, the order of testing is specified by the equation. META II like other programming languages would overflow its stack attempting left recursion. META II uses a $ (zero or more) sequence operator. The expr parsing equation written in META II is a conditional expression evaluated left to right:
Above the expr equation is defined by the expression to the right of the '='. Evaluating left to right from the '=', term is the first thing that must be tested. If term returns failure expr fails. If successful a term was recognized we then enter the indefinite $ zero or more loop were we first test for a '+' if that fails the alternative '-' is attempted and finally if a '-' were not recognized the loop terminates with expr returning success having recognized a single term. If a '+' or '-' were successful then term would be called. And if successful the loop would repeat. The expr equation can also be expressed using nested grouping as:
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META II AI simulator
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META II
META II is a domain-specific programming language for writing compilers. It was created in 1963–1964 by Dewey Val Schorre at University of California, Los Angeles (UCLA). META II uses what Schorre called syntax equations. Its operation is simply explained as:
Each syntax equation is translated into a recursive subroutine which tests the input string for a particular phrase structure, and deletes it if found.
Meta II programs are compiled into an interpreted byte code language. VALGOL and SMALGOL compilers illustrating its capabilities were written in the META II language, VALGOL is a simple algebraic language designed for the purpose of illustrating META II. SMALGOL was a fairly large subset of ALGOL 60.
META II was first written in META I, a hand-compiled version of META II. The history is unclear as to whether META I was a full implementation of META II or a required subset of the META II language required to compile the full META II compiler.
In its documentation, META II is described as resembling Backus–Naur form (BNF), which today is explained as a production grammar. META II is an analytical grammar. In the TREE-META document, these languages were described as reductive grammars.
For example, in BNF, an arithmetic expression may be defined as:
BNF rules are today production rules describing how constituent parts may be assembled to form only valid language constructs. A parser does the opposite taking language constructs apart. META II is a stack-based functional parser programming language that includes output directive. In META II, the order of testing is specified by the equation. META II like other programming languages would overflow its stack attempting left recursion. META II uses a $ (zero or more) sequence operator. The expr parsing equation written in META II is a conditional expression evaluated left to right:
Above the expr equation is defined by the expression to the right of the '='. Evaluating left to right from the '=', term is the first thing that must be tested. If term returns failure expr fails. If successful a term was recognized we then enter the indefinite $ zero or more loop were we first test for a '+' if that fails the alternative '-' is attempted and finally if a '-' were not recognized the loop terminates with expr returning success having recognized a single term. If a '+' or '-' were successful then term would be called. And if successful the loop would repeat. The expr equation can also be expressed using nested grouping as: