/usr/local/lib/swipl/library/aggregate.pl
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  • swipl
    • library
      • error.pl
      • debug.pl
      • apply.pl
      • lists.pl
      • broadcast.pl
      • predicate_options.pl
      • shlib.pl
      • option.pl
      • thread_pool.pl
      • gensym.pl
      • settings.pl
      • arithmetic.pl
      • main.pl
      • readutil.pl
      • operators.pl -- Manage operators
      • pairs.pl -- Operations on key-value lists
      • prolog_source.pl -- Examine Prolog source-files
      • record.pl -- Access compound arguments by name
      • quasi_quotations.pl -- Define Quasi Quotation syntax
      • pure_input.pl -- Pure Input from files and streams
      • solution_sequences.pl -- Modify solution sequences
      • ordsets.pl -- Ordered set manipulation
      • random.pl -- Random numbers
      • base64.pl -- Base64 encoding and decoding
      • aggregate.pl -- Aggregation operators on backtrackable predicates
        • safe_meta/2
        • aggregate/3
        • aggregate/4
        • aggregate_all/3
        • aggregate_all/4
        • foldall/4
        • foreach/2
        • free_variables/4
      • yall.pl -- Lambda expressions
      • sandbox.pl -- Sandboxed Prolog code
      • apply_macros.pl -- Goal expansion rules to avoid meta-calling
      • assoc.pl -- Binary associations
      • prolog_format.pl -- Analyse format specifications
      • csv.pl -- Process CSV (Comma-Separated Values) data
      • pprint.pl -- Pretty Print Prolog terms
      • atom.pl -- Operations on atoms
      • modules.pl -- Module utility predicates
      • occurs.pl -- Finding and counting sub-terms
      • prolog_xref.pl -- Prolog cross-referencer data collection
      • prolog_colour.pl
      • lazy_lists.pl -- Lazy list handling
      • ugraphs.pl -- Graph manipulation library
      • iostream.pl -- Utilities to deal with streams
      • url.pl -- Analysing and constructing URL
      • www_browser.pl -- Open a URL in the users browser
      • prolog_pack.pl -- A package manager for Prolog
      • git.pl -- Run GIT commands
      • utf8.pl -- UTF-8 encoding/decoding on lists of character codes.
      • dialect.pl -- Support multiple Prolog dialects
      • system.pl -- System utilities
      • terms.pl -- Term manipulation
      • date.pl -- Process dates and times
      • persistency.pl -- Provide persistent dynamic predicates
      • prolog_stack.pl -- Examine the Prolog stack
      • edinburgh.pl -- Some traditional Edinburgh predicates
      • prolog_clause.pl -- Get detailed source-information about a clause
      • prolog_breakpoints.pl -- Manage Prolog break-points
      • wfs.pl -- Well Founded Semantics interface
      • prolog_code.pl -- Utilities for reasoning about code
      • sort.pl
      • dicts.pl -- Dict utilities
      • dif.pl -- The dif/2 constraint
      • varnumbers.pl -- Utilities for numbered terms
      • pio.pl -- Pure I/O
      • zip.pl -- Access resource ZIP archives
 free_variables(:Generator, +Template, +VarList0, -VarList) is det
Find free variables in bagof/setof template. In order to handle variables properly, we have to find all the universally quantified variables in the Generator. All variables as yet unbound are universally quantified, unless
  1. they occur in the template
  2. they are bound by X^P, setof/3, or bagof/3

free_variables(Generator, Template, OldList, NewList) finds this set using OldList as an accumulator.

author
- Richard O'Keefe
- Jan Wielemaker (made some SWI-Prolog enhancements)
license
- Public domain (from DEC10 library).
To be done
- Distinguish between control-structures and data terms.
- Exploit our built-in term_variables/2 at some places?