M-expression
Proposed syntax for the Lisp language / From Wikipedia, the free encyclopedia
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In computer programming, M-expressions (or meta-expressions) were an early proposed syntax for the Lisp programming language, inspired by contemporary languages such as Fortran and ALGOL. The notation was never implemented into the language and, as such, it was never finalized.[1]
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M-expressions are a syntax for LISP code and provide function notation, syntax for a cond
form and for embedded literal data (via S-expressions) into programs. Thus M-Expressions used S-Expressions for literal data. The syntax for S-Expressions ("The Data Language") and M-Expressions ("The Meta Language") is defined on pages 8 and 9 of the Lisp 1.5 manual.[2]
M-Expressions also had a corresponding S-Expression representation. Code was manually translated from M-Expressions to S-Expressions. The in M-expressions embedded literal data, then had to be quoted in S-Expressions.
The M-Expression form
append[listvar;(PARIS BERLIN NEWYORK TOKYO)]
then needs to be transformed to the S-Expression form
(APPEND LISTVAR (QUOTE (PARIS BERLIN NEWYORK TOKYO)))