SWI-Prolog 9.3.21
All Application Manual Name SummaryHelp

All predicatesShow sourcepprint.pl -- Pretty Print Prolog terms

This module is a first start of what should become a full-featured pretty printer for Prolog terms with many options and parameters. Eventually, it should replace portray_clause/1 and various other special-purpose predicates.

To be done
- This is just a quicky. We need proper handling of portray/1, avoid printing very long terms multiple times, spacing (around operators), etc.
- Use a record for the option-processing.
- The current approach is far too simple, often resulting in illegal terms.
Source print_term(+Term, +Options) is det
Pretty print a Prolog term. The following options are processed:
output(+Stream)
Define the output stream. Default is user_output
right_margin(?Column)
Width of a line. If the output is a tty and tty_size/2 can produce a size the default is the number of columns minus 8. Otherwise the default is 72 characters. If the Column is unbound it is unified with the computed value.
left_margin(+Integer)
Left margin for continuation lines. Default is the current line position or 0 if that is not available.
tab_width(+Integer)
Distance between tab-stops. Default is 8 characters.
indent_arguments(+Spec)
Defines how arguments of compound terms are placed. Defined values are:
  • false
    Simply place them left to right (no line-breaks)
  • true
    Place them vertically, aligned with the open bracket (not implemented)
  • auto (default)
    As horizontal if line-width is not exceeded, vertical otherwise. See also auto_indent_arguments(Int)
  • An integer
    Place them vertically aligned, <N> spaces to the right of the beginning of the head.
auto_indent_arguments(+Integer)
Used by indent_arguments(auto) to decide whether to introduce a newline after the `(` or not. If specified and > 0, this provides the default integer for indent_arguments(Int). The "hanging" mode is used if otherwise the indentation increment is twice this value.
operators(+Boolean)
Deprecated. This is the inverse of the write_term/3 option ignore_ops. Default is to respect them. If either operators or the ignore_ops in write_options is specified, both are consistently set. If both are specified, the ignore_ops options in the write_options is respected.
write_options(+List)
List of options passed to write_term/3 for terms that are not further processed. Default: 
    [ numbervars(true),
      quoted(true),
      portray(true)
    ]
fullstop(Boolean)
If true (default false), add a full stop (.) to the output.
nl(Boolean)
If true (default false), add a newline to the output.
Source prepare_term(+Term, -Template, -Cycles, -Constraints)[private]
Prepare a term, possibly holding cycles and constraints for printing.
Source infix_list(+Term, ?Op, -List) is semidet[private]
True when List is a list of subterms of Term that are the result of the nested infix operator Op. Deals both with xfy and yfx operators.
Source pp_list_elements(+List, +Ctx, +Options) is det[private]
Print the elements of a possibly open list as a vertical list.
Source indent(+Out, +Indent, +Options)[private]
Newline and indent to the indicated column. Respects the option tab_width. Default is 8. If the tab-width equals zero, indentation is emitted using spaces.
Source print_width(+Term, -W, +Options) is det[private]
Width required when printing `normally' left-to-right.
Source pprint(+Term, +Context, +Options)[private]
The bottom-line print-routine.
Source is_op1(+Name, -Type, -Priority, -ArgPriority, +Options) is semidet[private]
True if Name is an operator taking one argument of Type.
Source is_op2(+Name, -LeftPri, -Pri, -RightPri, +Options) is semidet[private]
True if Name is an operator taking two arguments of Type.
Source need_space(@Term1, @Term2, +LeftOptions, +RightOptions)[private]
True if a space is needed between Term1 and Term2 if they are printed using the given option lists.
Source end_code_type(+Term, -Code, Options)[private]
True when code is the first/last character code that is emitted by printing Term using Options.
Source primitive(+Term, -Class) is semidet[private]
True if Term is a primitive term, rendered using the CSS class Class.
Source operator_module(-Module, +Options) is det[private]
Find the module for evaluating operators.
Source arg_options(+Options, -OptionsOut) is det[private]
Increment depth in Options.