Backtracking INTERCAL

Backtracking INTERCAL is an extension of INTERCAL by Malcolm Ryan to include backtracking like in Prolog.

• A MAYBE tag on a statement creates a choice point, containing the entire state of the program except ABSTAIN/REINSTATE status, after which the statement is performed normally.
• A GO BACK statement backtracks to the most recent choice point, redoing the statement in the negated sense, ignoring it if it is active and performing it if it is abstained from.
• A GO AHEAD statement eliminates the most recent choice point from the stack.

See also

• Threaded INTERCAL
• POGA-INTERCAL
• Backtracking INTERCAL was implemented in version 0.25 of C-INTERCAL.

External resources

• Malcolm Ryan's Intercal Extensions (from the Wayback Machine; retrieved on 23 March 2016)