P. Wadler. A critique of Abelson and Sussman or why calculating is better than scheming. Sigplan Notices, 22, No. 3:83{ 94, 1987. 10  Home/Search   Document Not in Database   Summary   Related Articles   Check

....eval, however, is of no consequence. The same e ect can be achieved if the decoding occurs after the explicit application of the eval operator. This encapsulates the decoding within the operator which requires it and insulates non metalinguistic applications from its widely noted ill e ects (cf. [Smi84, FW84, Wad87, Ada87]) Analogous remarks may be made about fexprs which provide explicit access to representations. Accordingly, M LISP s interfaces between the language and metalanguage eval and fexprs will localize the shifting between levels of representation which are performed globally in S expression LISP ....

P. Wadler. A critique of Abelson and Sussman or why calculating is better than scheming. Sigplan Notices, 22, No. 3:83{ 94, 1987. 10

....operational semantics. On the face of it this seems quite reasonable since Scheme correctly avoids the use of quotation in expressing higher order functions. But higher order functions in S expression LISP are only one of a number of desirable programming language features arising from 4 Wadler [Wad87], for example, notes that when students were asked to determine the value of the expression (car (quote (a . b) some responded that the value was quote, some that the value was the symbol a, and still others that it was the value of the variable named by the symbol a whatever that might be. ....

.... since these are the only operators which require dynamic conversion between programs and their representations, we can encapsulate the conversions within these operators thereby insulating the vast majority of non metalinguistic applications from the conversion s widely noted ill e ects (cf. [Smi84, FW84, Wad87, Ada]) 3 M LISP Motivated by the concerns described in the preceding section we are led to propose the following hybrid of the abstract syntaxes of M expression LISP and Scheme: M : X j [ j [M : M ] j x j ( x:M) j (M M) j (IF M M M) We have arrived at the syntax of the familiar untyped ....

P. Wadler. A critique of abelson and sussman or why calculating is better than scheming. In ACM SIGPLAN Notices, volume 22, 3, pages 83-94, 1987. 28

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