1Diffing(3)                       OCaml library                      Diffing(3)
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NAME

6       Diffing - Parametric diffing
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Module

9       Module   Diffing
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Documentation

12       Module Diffing
13        : sig end
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16       Parametric diffing
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18       This  module implements diffing over lists of arbitrary content.  It is
19       parameterized by
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21       -The content of the two lists
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23       -The equality witness when an element is kept
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25       -The diffing witness when an element is changed
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27       Diffing is extended to maintain state depending on the computed changes
28       while walking through the two lists.
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30       The  underlying  algorithm  is a modified Wagner-Fischer algorithm (see
31       <https://en.wikipedia.org/wiki/Wagner%E2%80%93Fischer_algorithm>).
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33       We provide the following guarantee: Given two lists l and r ,  if  dif‐
34       ferent  patches  result  in different states, we say that the state di‐
35       verges.
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37       -We always return the optimal patch on prefixes of l  and  r  on  which
38       state does not diverge.
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40       -Otherwise,  we return a correct but non-optimal patch where subpatches
41       with no divergent states are optimal for the given initial state.
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43       More precisely, the optimality of Wagner-Fischer depends on  the  prop‐
44       erty  that the edit-distance between a k-prefix of the left input and a
45       l-prefix of the right input d(k,l) satisfies
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47       d(k,l) = min ( del_cost + d(k-1,l), insert_cost + d(k,l-1), change_cost
48       + d(k-1,l-1) )
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50       Under  this  hypothesis,  it is optimal to choose greedily the state of
51       the minimal patch transforming the left k-prefix into the right  l-pre‐
52       fix  as  a  representative of the states of all possible patches trans‐
53       forming the left k-prefix into the right l-prefix.
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55       If this property is not satisfied, we can still choose greedily a  rep‐
56       resentative state. However, the computed patch is no more guaranteed to
57       be globally optimal.  Nevertheless, it is still a correct patch,  which
58       is even optimal among all explored patches.
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64       module type Defs = sig end
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67       The core types of a diffing implementation
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70       type change_kind =
71        | Deletion
72        | Insertion
73        | Modification
74        | Preservation
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77       The  kind of changes which is used to share printing and styling across
78       implementation
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82       val prefix : Format.formatter -> int * change_kind -> unit
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87       val style : change_kind -> Misc.Color.style list
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91       type ('left, 'right, 'eq, 'diff) change =
92        | Delete of 'left
93        | Insert of 'right
94        | Keep of 'left * 'right * 'eq
95        | Change of 'left * 'right * 'diff
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101       val classify : ('a, 'b, 'c, 'd) change -> change_kind
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105       module Define : functor (D : Defs) -> sig end
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109       Define(Defs) creates the diffing types from the types defined  in  Defs
110       and  the  functors  that need to be instantatied with the diffing algo‐
111       rithm parameters
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117OCamldoc                          2023-01-23                        Diffing(3)