INTERFACE\subsubsection{Runs}MTextUnit ; IMPORT MText, ISOChar; TYPE T = MText.T; (* This module imposes structure on character sequences in an "MText.T". There are three different structures supported: {\it runs}, {\it lines}, and {\it paragraphs}. Each structure defines a {\it unit}, in such a way that the entire mtext can be viewed as a sequence of non-overlapping units, possibly separated by characters that belong to no unit. A {\it run} is defined by a set of characters, typically "ISOChar.AlphaNumerics". A unit then corresponds to a ``word'', and the mtext is seen as a sequence of ``words'' separated by ``non-word'' characters. A {\it line} is defined as a set of characters delimited by newlines. A unit corresponds to a single line. The mtext is viewed as a sequence of lines with 0-length separators. A {\it paragraph} is a maximal sequence of non-blank lines. Given an index "n" into the text, we define the {\it extent} "e" for runs, lines, and paragraphs as a record containing the left and right boundaries of the unit surrounding the index, plus a boolean value indicating whether the character at position "n" is inside a unit or between units. Normally, "e.left <= index < e.right". The only exception is when "index" is greater than or equal to the length of the text, in which case "e.left = e.right = length" and "e.inside = FALSE". There are also utilities for handling blank lines and for finding the leading and trailing blanks on a line. If you pass an index that's less than 0, it is treated as 0; if you pass an index that's greater than the length of the text, it is treated as the length of the text. *) (* {\it Note for future work: There is nothing in the nature of runs, lines, and paragraphs that is specific to "MText.T". It would be at least as useful to provide this same functionality for "TEXT", "ARRAY" "OF CHAR", and seekable readers.} *) CONST WordRun = ISOChar.AlphaNumerics; BlankRun = ISOChar.Spaces; (* {' ', '\n', '\t', '\r', '\f'} *) NonBlankRun = ISOChar.All - BlankRun; TYPE Extent = RECORD left, right: INTEGER; inside : BOOLEAN END;
PROCEDURE RunExtent ( t : T; index : INTEGER; READONLY includedChars := WordRun): Extent; PROCEDURE StartOfRun (t : T; index: INTEGER; READONLY includedChars := WordRun): INTEGER;
Return the largesti <= index
for whichIsStartOfRun(t, i, includedChars)
isTRUE
. Return-1
if there is no suchi
.
PROCEDURE IsStartOfRun (t : T; index: INTEGER; READONLY includedChars := WordRun): BOOLEAN;
Equivalent toWITH e = RunExtent(t, index, includedChars) DO RETURN e.inside AND e.left = index END
PROCEDURE EndOfRun (t : T; index: INTEGER; READONLY includedChars := WordRun): INTEGER;
Return the smallesti >= index
for whichIsEndOfRun(t, i, includedChars)
isTRUE
. Return-1
if there is no suchi
.
PROCEDURE IsEndOfRun (t : T; index: INTEGER; READONLY includedChars := WordRun): BOOLEAN;
Equivalent toWITH e = RunExtent(t, index, includedChars) DO RETURN NOT e.inside AND e.left = index ENDorIsStartOfRun(t, index, ISOChar.All - includedChars)
\subsubsection{Lines}
TYPE LineOption = {ExcludeBlanks, IncludeBlanks, IncludeNewline};A {\it line} is a sequence of characters delimited by newlines (or the mtext boundaries). The client may specify a subsequence of the line by passing left and right ``line options.'' If the left option is
ExcludeBlanks
, then
the subsequence will not include any initial blanks. If the
left option is IncludeBlanks
, then it will. If the left
option is IncludeNewline
, it will be treated the same as
IncludeBlanks
.
If the right option is ExcludeBlanks
, then the subsequence
will not include any trailing blanks. If the right option is
IncludeBlanks
, then it will. If the right option is
IncludeNewline
, then it will include both the trailing
blanks and the following newline.
The default left option is IncludeBlanks
; the default right
option is IncludeNewline
. This is consistent with the view
of the text as a sequence of lines, with no intermediate
``gaps.''
PROCEDURE LineExtent (t: T; index: INTEGER): Extent;
Compute the extent of the line surrounding index. If a newline immediately precedes index, it uses the line that begins at index, not the one that ends there.LineExtent(t, index).inside
is alwaysTRUE
.
TYPE LineRec = RECORD left : INTEGER; (* start of line *) leftMargin : INTEGER; (* first non-blank *) rightMargin: INTEGER; (* 1 + last non-blank *) rightEnd : INTEGER; (* final newline *) right : INTEGER; (* rightEnd + 1 *) END;
ALineRec
contains the positions within a line. Normally,
left <= leftMargin <= rightMargin <= rightEndandright = rightEnd + 1
, i.e., theleft
of the next line, but there are exceptions. On a line consisting entirely of blanks (at least one),
left < leftMargin = rightMargin = rightEndOn the last line of the file (following the last newline),right = rightEnd
.If
index = length(t)
and there is a newline immediately precedingindex
, then all 5 values will be equal toindex
.
PROCEDURE LineInfo (t: T; index: INTEGER): LineRec; PROCEDURE LineFacts ( t : T; index : INTEGER; VAR (* out *) left : INTEGER; VAR (* out *) leftMargin : INTEGER; VAR (* out *) rightMargin: INTEGER; VAR (* out *) rightEnd : INTEGER; VAR (* out *) right : INTEGER ); PROCEDURE StartOfLine (t : T; index: INTEGER; leftOption := LineOption.IncludeBlanks): INTEGER;
IFleftOption = ExcludeBlanks
, then returnLineInfo(t, index).leftMargin
. Otherwise returnLineInfo(t, index).left
.
PROCEDURE IsStartOfLine (t : T; index: INTEGER; leftOption := LineOption.IncludeBlanks): BOOLEAN;
Return index = StartOfLine(t, index, leftOption)
PROCEDURE EndOfLine (t : T; index: INTEGER; rightOption := LineOption.IncludeNewline): INTEGER;
Return therightMargin
,rightEnd
, orright
field ofLineInfo(t, index)
, depending on whetherrightOption
isExcludeBlanks
,IncludeBlanks
, orIncludeNewline
, respectively.
PROCEDURE IsEndOfLine (t : T; index: INTEGER; rightOption := LineOption.IncludeNewline): BOOLEAN;
Return index = EndOfLine (t, index, rightOption)
\subsubsection{Blank lines}
PROCEDURE IsBlankLine (t: T; index: INTEGER): BOOLEAN;
ReturnTRUE
ifindex
is located on a line that consists entirely of blanks, tabs, and form-feeds, including empty lines.
PROCEDURE BlankLinesExtent (t: T; ndex: INTEGER): Extent;
Computes the extent of maximal sequence of blank lines
surrounding index
.
\subsubsection{Paragraphs}
A {\it paragraph} is a maximal sequence of non-blank lines, in
the sense of LineExtent
where the left option is
IncludeBlanks
and the right option is IncludeNewline
.
PROCEDURE ParagraphExtent (t: T; index: INTEGER): Extent; PROCEDURE StartOfParagraph (t: T; index: INTEGER): INTEGER;
Return the largesti <= index
for whichIsStartOfParagraph(t, i)
isTRUE
. Return-1
if there is no suchi
.
PROCEDURE IsStartOfParagraph (t: T; index: INTEGER): BOOLEAN;
Equivalent toWITH e = ParagraphExtent(t, index) DO RETURN e.inside AND e.left = index END
PROCEDURE EndOfParagraph (t: T; index: INTEGER): INTEGER;
Return the smallesti >= index
for whichIsEndOfParagraph(t, i)
isTRUE
. Return-1
if there is no suchi
.
PROCEDURE IsEndOfParagraph (t: T; index: INTEGER): BOOLEAN;
Equivalent toWITH e = ParagraphExtent(t, index) DO RETURN NOT e.inside AND e.left = index END
END MTextUnit.