Changeset 931f1b4 for doc/theses/mike_brooks_MMath/string.tex

Timestamp:

Apr 10, 2025, 7:31:11 AM (5 months ago)

Author:

Peter A. Buhr <pabuhr@…>

Branches:

master

Children:

9018dcf

Parents:

d914750

Message:

more proofreading string chapter

File:

• doc/theses/mike_brooks_MMath/string.tex (modified) (5 diffs)

doc/theses/mike_brooks_MMath/string.tex

@@ -7 +7 @@
 
 \section{String Operations}
+
+% https://en.wikipedia.org/wiki/Comparison_of_programming_languages_(string_functions)
 
 \VRef[Figure]{f:StrApiCompare} shows a general comparison of string APIs for C, \CC, Java and \CFA.
@@ -23 +25 @@
 @strlen@                                & @length@, @size@              & @length@                      & @size@        \\
 @[ ]@                                   & @[ ]@                                 & @charAt@          & @[ ]@     \\
-@strncpy@                               & @substr@                              & @substring@       & @( )@     \\
-@strncpy@                               & @replace@                             & @replace@         & @=@ \emph{(on a substring)}\\
+@strncpy@                               & @substr@                              & @substring@       & @( )@ RHS @=@     \\
+@strncpy@                               & @replace@                             & @replace@         & @( )@ LHS @=@ \\
 @strstr@                                & @find@                                & @indexOf@         & @find@ \\
 @strcspn@                               & @find_first_of@               & @matches@         & @include@ \\
@@ -62 +64 @@
 \begin{cquote}
 \sf
-\begin{tabular}{@{}rrrrrl@{}}
-\small\tt a & \small\tt b & \small\tt c & \small\tt d & \small\tt e \\
+\begin{tabular}{@{}rrrrll@{}}
+\small\tt "a & \small\tt b & \small\tt c & \small\tt d & \small\tt e" \\
 0 & 1 & 2 & 3 & 4 & left to right index \\
 -5 & -4 & -3 & -2 & -1 & right to left index
@@ -72 +74 @@
 \begin{cfa}
 #include @<string.hfa>@
-@string@ s = "abcde", name = "MIKE", digit, alpha, punctuation, ifstmt;
+@string@ s = "abcde", name = "MIKE", digit = "0123456789";
 const char cs[] = "abc";
 int i;
-digit  = "0123456789";
-punctuation = "().,";
-ifstmt = "IF (A > B) {";
-\end{cfa}
-Note, the include file @string.hfa@ to access type @string@.
+\end{cfa}
+Note, the include file @<string.hfa>@ to access type @string@.
 
 
@@ -394 +393 @@
 Extending the pattern to a regular expression is a possible extension.
 
-
-\subsection{Searching}
-
-The @index@ operation
-\begin{cfa}
-int index( const string & key, int start = 1, occurrence occ = first );
-\end{cfa}
-returns the position of the first or last occurrence of the @key@ (depending on the occurrence indicator @occ@ that is either @first@ or @last@) in the current string starting the search at position @start@.
-If the @key@ does not appear in the current string, the length of the current string plus one is returned.
-%If the @key@ has zero length, the value 1 is returned regardless of what the current string contains.
-A negative starting position is a specification from the right end of the string.
+The replace operation returns a string in which all occurrences of a substring are replaced by another string.
 \begin{cquote}
 \setlength{\tabcolsep}{15pt}
 \begin{tabular}{@{}l|l@{}}
 \begin{cfa}
-i = find( digit, "567" );
-i = find( digit, "567", 7 );
-i = digit.index( "567", -1, last );
-i = name.index( "E", 5, last );
-\end{cfa}
-&
-\begin{cfa}
+s = replace( "PETER", "E", "XX" );
+s = replace( "PETER", "ET", "XX" );
+s = replace( "PETER", "W", "XX" );
+\end{cfa}
+&
+\begin{cfa}
+"PXXTXXR"
+"PXXER"
+"PETER"
+\end{cfa}
+\end{tabular}
+\end{cquote}
+The replacement is done left-to-right and substituted text is not examined for replacement.
+
+
+\subsection{Searching}
+
+The find operation returns the position of the first occurrence of a key string in a string.
+If the key does not appear in the current string, the length of the current string plus one is returned.
+\begin{cquote}
+\setlength{\tabcolsep}{15pt}
+\begin{tabular}{@{}l|l@{}}
+\begin{cfa}
+i = find( digit, '3' );
+i = "45" ^ digit; // python style "45" in digit
+string x = "567";
+i = find( digit, x );
+\end{cfa}
+&
+\begin{cfa}
+3
+4
+
 5
-10
-
-
-\end{cfa}
-\end{tabular}
-\end{cquote}
-The next two string operations test a string to see if it is or is not composed completely of a particular class of characters.
-For example, are the characters of a string all alphabetic or all numeric?
-Use of these operations involves a two step operation.
-First, it is necessary to create an instance of type @strmask@ and initialize it to a string containing the characters of the particular character class, as in:
-\begin{cfa}
-strmask digitmask = digit;
-strmask alphamask = string( "abcdefghijklmnopqrstuvwxyz" );
-\end{cfa}
-Second, the character mask is used in the functions @include@ and @exclude@ to check a string for compliance of its characters with the characters indicated by the mask.
-
-The @include@ operation
-\begin{cfa}
-int include( const strmask &, int = 1, occurrence occ = first );
-\end{cfa}
-returns the position of the first or last character (depending on the occurrence indicator, which is either @first@ or @last@) in the current string that does not appear in the @mask@ starting the search at position @start@;
-hence it skips over characters in the current string that are included (in) the @mask@.
-The characters in the current string do not have to be in the same order as the @mask@.
-If all the characters in the current string appear in the @mask@, the length of the current string plus one is returned, regardless of which occurrence is being searched for.
-A negative starting position is a specification from the right end of the string.
-\begin{cfa}
-i = name.include( digitmask );          $\C{// i is assigned 1}$
-i = name.include( alphamask );          $\C{// i is assigned 6}$
-\end{cfa}
-
-The @exclude@ operation
-\begin{cfa}
-int exclude( string &mask, int start = 1, occurrence occ = first )
-\end{cfa}
-returns the position of the first or last character (depending on the occurrence indicator, which is either @first@ or @last@) in the current string that does appear in the @mask@ string starting the search at position @start@;
-hence it skips over characters in the current string that are excluded from (not in) in the @mask@ string.
-The characters in the current string do not have to be in the same order as the @mask@ string.
-If all the characters in the current string do NOT appear in the @mask@ string, the length of the current string plus one is returned, regardless of which occurrence is being searched for.
-A negative starting position is a specification from the right end of the string.
-\begin{cfa}
-i = name.exclude( digitmask );          $\C{// i is assigned 6}$
-i = ifstmt.exclude( strmask( punctuation ) ); $\C{// i is assigned 4}$
-\end{cfa}
-
-The @includeStr@ operation:
-\begin{cfa}
-string includeStr( strmask &mask, int start = 1, occurrence occ = first )
-\end{cfa}
-returns the longest substring of leading or trailing characters (depending on the occurrence indicator, which is either @first@ or @last@) of the current string that ARE included in the @mask@ string starting the search at position @start@.
-A negative starting position is a specification from the right end of the string.
-\begin{cfa}
-s = name.includeStr( alphamask );       $\C{// s is assigned "MIKE"}$
-s = ifstmt.includeStr( alphamask );     $\C{// s is assigned "IF"}$
-s = name.includeStr( digitmask );       $\C{// s is assigned ""}$
-\end{cfa}
-
-The @excludeStr@ operation:
-\begin{cfa}
-string excludeStr( strmask &mask, int start = 1, occurrence = first )
-\end{cfa}
-returns the longest substring of leading or trailing characters (depending on the occurrence indicator, which is either @first@ or @last@) of the current string that are excluded (NOT) in the @mask@ string starting the search at position @start@.
-A negative starting position is a specification from the right end of the string.
-\begin{cfa}
-s = name.excludeStr( digitmask);        $\C{// s is assigned "MIKE"}$
-s = ifstmt.excludeStr( strmask( punctuation ) ); $\C{// s is assigned "IF "}$
-s = name.excludeStr( alphamask);        $\C{// s is assigned ""}$
-\end{cfa}
-
-
-\subsection{Miscellaneous}
-
-The @trim@ operation
-\begin{cfa}
-string trim( string &mask, occurrence occ = first )
-\end{cfa}
-returns a string in that is the longest substring of leading or trailing characters (depending on the occurrence indicator, which is either @first@ or @last@) which ARE included in the @mask@ are removed.
-\begin{cfa}
-// remove leading blanks
-s = string( "   ABC" ).trim( " " );     $\C{// s is assigned "ABC",}$
-// remove trailing blanks
-s = string( "ABC   " ).trim( " ", last ); $\C{// s is assigned "ABC",}$
-\end{cfa}
-
-The @translate@ operation
-\begin{cfa}
-string translate( string &from, string &to )
-\end{cfa}
-returns a string that is the same length as the original string in which all occurrences of the characters that appear in the @from@ string have been translated into their corresponding character in the @to@ string.
-Translation is done on a character by character basis between the @from@ and @to@ strings; hence these two strings must be the same length.
-If a character in the original string does not appear in the @from@ string, then it simply appears as is in the resulting string.
-\begin{cfa}
-// upper to lower case
-name = name.translate( "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "abcdefghijklmnopqrstuvwxyz" );
-                        // name is assigned "name"
-s = ifstmt.translate( "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "abcdefghijklmnopqrstuvwxyz" );
-                        // ifstmt is assigned "if (a > b) {"
-// lower to upper case
-name = name.translate( "abcdefghijklmnopqrstuvwxyz", "ABCDEFGHIJKLMNOPQRSTUVWXYZ" );
-                        // name is assigned "MIKE"
-\end{cfa}
-
-The @replace@ operation
-\begin{cfa}
-string replace( string &from, string &to )
-\end{cfa}
-returns a string in which all occurrences of the @from@ string in the current string have been replaced by the @to@ string.
-\begin{cfa}
-s = name.replace( "E", "XX" );          $\C{// s is assigned "PXXTXXR"}$
-\end{cfa}
-The replacement is done left-to-right.
-When an instance of the @from@ string is found and changed to the @to@ string, it is NOT examined again for further replacement.
+\end{cfa}
+\end{tabular}
+\end{cquote}
+The character-class operations indicates if a string is composed completely of a particular class of characters, \eg, alphabetic, numeric, vowels, \etc.
+\begin{cquote}
+\setlength{\tabcolsep}{15pt}
+\begin{tabular}{@{}l|l@{}}
+\begin{cfa}
+charclass vowels{ "aeiouy" };
+i = include( "aaeiuyoo", vowels );
+i = include( "aabiuyoo", vowels );
+\end{cfa}
+&
+\begin{cfa}
+
+8  // compliant
+2  // b non-compliant
+\end{cfa}
+\end{tabular}
+\end{cquote}
+@vowels@ defines a character class and function @include@ checks if all characters in the string are included in the class (compliance).
+The position of the last character plus 1 is return if the string is compliant or the position of the first non-compliant character.
+There is no relationship between the order of characters in the two strings.
+Function @exclude@ is the reverse of @include@, checking if all characters in the string are excluded from the class (compliance).
+\begin{cquote}
+\setlength{\tabcolsep}{15pt}
+\begin{tabular}{@{}l|l@{}}
+\begin{cfa}
+i = exclude( "cdbfghmk", vowels );
+i = exclude( "cdyfghmk", vowels );
+\end{cfa}
+&
+\begin{cfa}
+8  // compliant
+2  // y non-compliant
+\end{cfa}
+\end{tabular}
+\end{cquote}
+Both forms can return the longest substring of compliant characters.
+\begin{cquote}
+\setlength{\tabcolsep}{15pt}
+\begin{tabular}{@{}l|l@{}}
+\begin{cfa}
+s = include( "aaeiuyoo", vowels );
+s = include( "aabiuyoo", vowels );
+s = exclude( "cdbfghmk", vowels );
+s = exclude( "cdyfghmk", vowels );
+\end{cfa}
+&
+\begin{cfa}
+"aaeiuyoo"
+"aa"
+"cdbfghmk"
+"cd"
+\end{cfa}
+\end{tabular}
+\end{cquote}
+
+The test operation checks if each character in a string is in one of the C character classes.
+\begin{cquote}
+\setlength{\tabcolsep}{15pt}
+\begin{tabular}{@{}l|l@{}}
+\begin{cfa}
+i = test( "1FeC34aB", @isxdigit@ );
+i = test( ".,;'!\"", @ispunct@ );
+i = test( "XXXx", @isupper@ );
+\end{cfa}
+&
+\begin{cfa}
+8   // compliant
+6   // compliant
+3   // non-compliant
+\end{cfa}
+\end{tabular}
+\end{cquote}
+The position of the last character plus 1 is return if the string is compliant or the position of the first non-compliant character.
+
+Combining substring and search allows actions like trimming whitespace from the start of a line.
+\begin{cquote}
+\setlength{\tabcolsep}{15pt}
+\begin{tabular}{@{}l|l@{}}
+\begin{cfa}
+string line = "  \t  xxx yyy zzz";
+string trim = line( test( line, isspace ) );
+\end{cfa}
+&
+\begin{cfa}
+
+"xxx yyy zzz"
+\end{cfa}
+\end{tabular}
+\end{cquote}
+
+The translate operation returns a string with each character transformed by one of the C character transformation functions.
+\begin{cquote}
+\setlength{\tabcolsep}{15pt}
+\begin{tabular}{@{}l|l@{}}
+\begin{cfa}
+s = translate( "abc", @toupper@ );
+s = translate( "ABC", @tolower@ );
+int tospace( int c ) { return isspace( c ) ? ' ' : c; }
+s = translate( "X X\tX\nX", @tospace@ );
+\end{cfa}
+&
+\begin{cfa}
+"ABC"
+"abc"
+
+"X X X X"
+\end{cfa}
+\end{tabular}
+\end{cquote}