Quote: backtracing primitives for recovery points (a 'tag'), with redo assignment, tentative assignment, and remove tag

Note

backtracking primitives tag(x) tag point keyed by x, fail (x,i,f) return to ith previous tag(x) and evaluate f in that environment. (redo tag(x assign (x,y) of x<=y, tentatively assign y to x (undone on fail across untag (x,i) remove tags from and including ith previous tag(x) optional args eg fail () fails previous tag point

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Topic: backtracking (30 items)