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  1. program LexicalAnalyzer;
  2.  
  3. function CheckFirstWord(s: string; var p: integer): boolean;
  4. var
  5.   start: integer;
  6. begin
  7.   start := p;
  8.  
  9.   { (000)* }
  10.   while (p + 2 <= Length(s)) and
  11.         (s[p] = '0') and
  12.         (s[p + 1] = '0') and
  13.         (s[p + 2] = '0') do
  14.     p := p + 3;
  15.  
  16.   { 001 }
  17.   if (p + 2 > Length(s)) or
  18.      (s[p] <> '0') or
  19.      (s[p + 1] <> '0') or
  20.      (s[p + 2] <> '1') then
  21.   begin
  22.     p := start;
  23.     CheckFirstWord := false;
  24.     Exit;
  25.   end;
  26.  
  27.   p := p + 3;
  28.  
  29.   { (010)* }
  30.   while (p + 2 <= Length(s)) and
  31.         (s[p] = '0') and
  32.         (s[p + 1] = '1') and
  33.         (s[p + 2] = '0') do
  34.     p := p + 3;
  35.  
  36.   CheckFirstWord := true;
  37. end;
  38.  
  39.  
  40. function CheckSecondWord(s: string; var p: integer): boolean;
  41. begin
  42.   { First two characters must be ab }
  43.  
  44.   if p + 1 > Length(s) then
  45.   begin
  46.     CheckSecondWord := false;
  47.     Exit;
  48.   end;
  49.  
  50.   if (s[p] <> 'a') or (s[p + 1] <> 'b') then
  51.   begin
  52.     CheckSecondWord := false;
  53.     Exit;
  54.   end;
  55.  
  56.   p := p + 2;
  57.  
  58.   { Other characters can be a, b, c or d }
  59.  
  60.   while (p <= Length(s)) and
  61.         (s[p] in ['a', 'b', 'c', 'd']) do
  62.     p := p + 1;
  63.  
  64.   CheckSecondWord := true;
  65. end;
  66.  
  67.  
  68. function AnalyzeLine(s: string; lineNumber: integer): boolean;
  69. var
  70.   p: integer;
  71.   ok: boolean;
  72. begin
  73.   p := 1;
  74.   AnalyzeLine := true;
  75.  
  76.   while p <= Length(s) do
  77.   begin
  78.  
  79.     { Skip spaces }
  80.     while (p <= Length(s)) and (s[p] = ' ') do
  81.       p := p + 1;
  82.  
  83.     if p > Length(s) then
  84.       Exit;
  85.  
  86.     { Comment }
  87.     if s[p] = '''' then
  88.     begin
  89.       Exit;
  90.     end;
  91.  
  92.     { First word }
  93.     if s[p] = '0' then
  94.     begin
  95.       ok := CheckFirstWord(s, p);
  96.  
  97.       if not ok then
  98.       begin
  99.         writeln('Error in line ', lineNumber,
  100.                 ', position ', p,
  101.                 ': invalid first word.');
  102.         AnalyzeLine := false;
  103.         Exit;
  104.       end;
  105.     end
  106.  
  107.     { Second word }
  108.     else if s[p] in ['a', 'b', 'c', 'd'] then
  109.     begin
  110.       ok := CheckSecondWord(s, p);
  111.  
  112.       if not ok then
  113.       begin
  114.         writeln('Error in line ', lineNumber,
  115.                 ', position ', p,
  116.                 ': invalid second word.');
  117.         AnalyzeLine := false;
  118.         Exit;
  119.       end;
  120.     end
  121.  
  122.     { Invalid character }
  123.     else
  124.     begin
  125.       writeln('Error in line ', lineNumber,
  126.               ', position ', p,
  127.               ': invalid character.');
  128.       AnalyzeLine := false;
  129.       Exit;
  130.     end;
  131.  
  132.   end;
  133. end;
  134.  
  135.  
  136. var
  137.   n: integer;
  138.   i: integer;
  139.   line: string;
  140.   allCorrect: boolean;
  141.  
  142. begin
  143.  
  144.   writeln('=============================================');
  145.   writeln('LEXICAL ANALYZER');
  146.   writeln('VARIANT 34');
  147.   writeln('=============================================');
  148.   writeln;
  149.  
  150.   writeln('WORD 1: (000)*001(010)*');
  151.   writeln('WORD 2: ab(a | b | c | d)*');
  152.   writeln('COMMENT: apostrophe to end of line');
  153.   writeln;
  154.  
  155.   write('Enter number of lines: ');
  156.   readln(n);
  157.  
  158.   writeln;
  159.   writeln('Enter text:');
  160.  
  161.   allCorrect := true;
  162.  
  163.   for i := 1 to n do
  164.   begin
  165.     readln(line);
  166.  
  167.     if not AnalyzeLine(line, i) then
  168.       allCorrect := false;
  169.   end;
  170.  
  171.   writeln;
  172.  
  173.   if allCorrect then
  174.     writeln('No errors found.');
  175.  
  176.   writeln;
  177.   writeln('Press Enter to exit.');
  178.   readln;
  179.  
  180. end.
Success #stdin #stdout 0s 5316KB
comments (?)
stdin
copy 
3
001 ab
000001010 abcd
' this is a comment
stdout
copy 
=============================================
LEXICAL ANALYZER
VARIANT 34
=============================================

WORD 1: (000)*001(010)*
WORD 2: ab(a | b | c | d)*
COMMENT: apostrophe to end of line

Enter number of lines: 
Enter text:

No errors found.

Press Enter to exit.
https://ideone.com/NNMzmu
language:
Pascal (fpc 3.0.4)
created:
1 hour ago
visibility:
public

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