ALGOL X was the code name given to the programming language which the Working Group 2.1 on ALGOL of the International Federation for Information Processing was to develop as a successor to ALGOL 60. It attempted to find a "short-term solution to existing difficulties".
According to de Morgan "... the Algol 60 devotees had not been idle... they set out to eliminate the dreaded Remaining Trouble Spots. They called their Algol 60 'Modified'."
One ALGOL X compiler is known to have existed, it was written with the AED-0 system ("Automated Engineering Design", also referred to as"ALGOL Extended for Design") by Douglas T. Ross of MIT.
Example class definition: (An extract from AB26.2.2)
class expression is constant (real value) ora variable (string printname) ora class pair is (sum ora difference ora product ora quotient)((expression) left operand, right operand, derivative);Example class usage:
(expression) X; (constant) Y; (pair) Z; (product) Q; X := Y:= constant(10.5); Z := Q := product(variable("ALPHA"), constant(2.), constant(2.))"Initially the proposal for an update to Algol was Algol X, with Algol Y being the name reserved for the corresponding metalanguage. Van Wijngaarden produced a paper for the 1963 IFIP programming language committee, entitled “Generalized Algol,” which contained the basic concepts which were eventually incorporated into Algol 68."[1]