Algol 60

6.11

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Algol 60

1 Implementation

The “Algol 60” language for DrRacket implements the language defined by the “Revised Report on the Algorithmic Language Algol 60,” edited by Peter Naur.

2 Including Algol 60 Programs

Although Algol 60 is mainly provided as a DrRacket language, include-algol supports limited use of Algol 60 programs in larger programs.

(require algol60/algol60)

package: algol60

syntax
(include-algol path-string)

Includes the Algol 60 program indicated by path-string as an expression in a Racket program. The included Algol 60 program is closed (i.e., it doesn’t see any bindings in the included context), and the result is always #<void>.

syntax
(literal-algol string ...)

Evaluates the Algol 60 program indicated by the literal strings as an expression in a Racket program. The Algol 60 program is closed (i.e., it doesn’t see any bindings in the included context), and the result is always #<void>.

This is generally useful when combined with the at-exp reader, e.g.,

#lang at-exp racket
@literal-algol{
  begin
    printsln (`hello world')
  end
}

3 Language

The DrRacket and include-algol implementation departs from the Algol 60 specification in the following minor ways:

Strings are not permitted to contain nested quotes.
Identifiers cannot contain whitespace.
Argument separators are constrained to be identifiers (i.e., they cannot be keywords, and they cannot consist of multiple identifiers separated by whitespace.)
Numbers containing exponents (using the “10” subscript) are not supported.

Identifiers and keywords are case-sensitive. The boldface/underlined keywords of the report are represented by the obvious character sequence, as are most operators. A few operators do not fit into ASCII, and they are mapped as follows:

times *

quotient div

exponential ^

less or equal <=

greater or equal >=

not equal !=

equivalence ==

implication =>

and &

or |

negation !

In addition to the standard functions, the following output functions are supported:

prints(E) prints the string E

printsln(E) prints the string E followed by a newline

printn(E) prints the number E

printnln(E) prints the number E followed by a newline

A prompt in DrRacket’s interactions area accepts whole programs only for the Algol 60 language.

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