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From: ram@zedat.fu-berlin.de (Stefan Ram)
Newsgroups: comp.text.tex
Subject: Re: TeX's line breaking in the grub sesh
Date: 28 Aug 2024 18:34:59 GMT
Organization: Stefan Ram
Lines: 127
Expires: 1 Jul 2025 11:59:58 GMT
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ram@zedat.fu-berlin.de (Stefan Ram) wrote or quoted:
>For sure there's some janky bugs in there, but peep this:

  Turns out there was still a glitch in the code! The latest
  build now shows a paragraph break with (fingers crossed)
  global optimization, taking parshape into account. Now that
  I've finally squashed the bug, discretionary items haven't
  been baked in yet. That's next on my to-do list though.

  Ironically, lines of the following Python 3.12 source code have NOT
  been wrapped to the 72 characters recommended for Usenet posts!

  main.py

from dataclasses import dataclass
from typing import Optional, List, Iterator
import bisect

source_text = list( ' Lorem ipsum dolor sit amet, consectetur adipiscing elit, '
'sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad '
'minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea '
'commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit '
'esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat '
'non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. ' )
                    
parshape =[ 80, 80, 80, 40 ]

@dataclass
class ActiveEntry:
    previous:    Optional[ 'ActiveEntry' ]= None
    position:    int = 0 # position in the text 
    branch:      int = 0 # for future version
    sum_quality: int = 0 # the sum of all "merits" up to this point
    line_number: int = 0 # line started with this (first line = 0)

parshape_length = len( parshape )

def print_up_to( this ):
    '''prints the wrapped paragraph up to the point "this".
    It starts at the back point "this" and then goes forward
    in the text via the linked chain of points. Finally, for
    printing the text in the normal order, it then goes forward
    again.'''
    buff = []
    qual = []
    sum_quality = this.sum_quality
    while this.previous:
        previous = this.previous
        line = source_text[ previous.position: this.position ]
        # print( f'{line = }' )
        buff.append( line )
        qual.append( this.sum_quality )
        this = previous
    start_position = 0
    # we went backwards, but actually want to print in the normal direction
    first = 1
    for i,( line, qual ) in enumerate( zip( reversed( buff ), reversed( qual ))):
        text = ''.join( line[ start_position: ])
        target_length = parshape[ i ]if i < parshape_length else parshape[ -1 ]# dupe!
        output = text
        print( output[ first: ])
        first = 0
        start_position = 1 # skip an initial space or something
    print()
    print( 'Total merits:', sum_quality )
    print()

active0 = ActiveEntry()
    
active_list =[ active0 ]

current_position = 1
source_length = len( source_text )
while current_position < len( source_text ):
    ch = source_text[ current_position ]
    if ch == ' ': # possible breakpoint
        new_active_list = [] # next active list
        best_sum_quality = None # best quality summed across this and previous lines, not yet determined
        best_act = active_list[ 0 ] # preliminary choice
        for active in active_list:
            active_position = active.position
            line_number = active.line_number
            target_length = parshape[ line_number ]if line_number < parshape_length else parshape[ -1 ]# dupe!
            distance = current_position - active_position
            adjustment = target_length - distance
            if adjustment < 0:
                #   "When an active breakpoint a is encountered for which
                #      the line from a to b has an adjustment ratio less 
                #      than -1 (that is, when the line can't be shrunk to 
                #      fit the desired length), breakpoint a is removed 
                #      from the active list."
                pass # do not transfer into the new active list
            else:
                new_active_list.append( active )
                this_line_quality = -adjustment**2
                have_reached_final_space = current_position == source_length - 1 # final ' ' on end of last line 
                if have_reached_final_space: this_line_quality = 0 # arbitrary whitespace at end is accepted
                this_sum_quality = active.sum_quality + this_line_quality
                if \
                best_sum_quality is None or \
                this_sum_quality > best_sum_quality:
                    best_sum_quality = this_sum_quality
                    best_predecessor = active
        if best_sum_quality is not None:
            # make a new active point from current position, linking it to the best active point found
            new_active_list.append( ActiveEntry( previous=best_predecessor, position=current_position, branch=0, sum_quality=best_sum_quality, line_number=best_predecessor.line_number+1 ))
        active_list = new_active_list
    current_position += 1
active = active_list[ -1 ] # the final space

print_up_to( active )

  output

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis
nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit
in voluptate velit esse cillum dolore
eu fugiat nulla pariatur. Excepteur
sint occaecat cupidatat non proident,
sunt in culpa qui officia deserunt
mollit anim id est laborum.

Total merits: -80