Pascal Infinite while loop

I'm implementing a program in FreePascal in Win10(64-bit). The problem state:

'Given a string, replace all substring 'child' with 'childhood' '

'Replace all 'child' with 'childhood''

I try this program

uses crt;

var s, newS : string;

    tmp, tmp2, tmp3 : int64;

    tmpstr, tmpstr2 : string;

    step, step2, step3 : longint;

    position : longint;



begin

        clrscr;

        write('Nhap xau : '); readln(s);

        //main mechanism



        while pos('child',s) <> 0 do begin

                position := pos('child', s);

                delete(s, pos('child',1), 5);

                insert('childhood',s,position);

                inc(position, 9);

                newS := '';

                for step:=position to length(s) do begin

                        newS := newS + s[step];

                end;

                s := newS;

        end;

        writeln(s);



        readkey;

end.

You can see that this part:

inc(position, 9);

newS := '';

for step:=position to length(s) do begin

        newS := newS + s[step];

end;

s := newS;

was used to try to cut off the while loop, but it doesn't work. Any idea?

Thanks a lot and have a good day! Thanks for reading this question thread! =)

asked Nov 23 '18 at 14:55

hungnguyen

378

1

Given the requirement is as you've stated, I suggest replacing your program with a call to StringReplace.

– Sertac Akyuz
Nov 23 '18 at 15:17

This is homework I guess. What your instructor is hoping is that you will debug your program to find out what is going wrong. Do you know how to debug? If not, there is no time like the present.

– David Heffernan
Nov 23 '18 at 15:20

1

I hope you are aware of the fact that the replacement 'childhood' contains the search text, 'child' and that this should have consequences for how and where you try to find your search text after you replaced it. Otherwise 'child' will become 'childhood', 'childhoodhood', 'childhoodhoodhood', etc. ad infinitum. So do as @David says, and debug your program. It is an important skill and easy to learn.

– Rudy Velthuis
Nov 23 '18 at 19:29

FWIW, since the line delete(s, pos('child',1), 5);probably doesn't compile at all, it looks as if this is not exactly your code. Please always post the exact code (copy and paste) that gives you problems. Do not type it from memory or from view. Use copy and paste. How can we tell what is wrong with your code if we don't even see your exact code? The error could just as well be in the in the part you typed wrongly.

– Rudy Velthuis
Nov 23 '18 at 19:33

@Rudy_Velthius this is my exact code. I copy paste from notepad

– hungnguyen
Nov 24 '18 at 2:54

|
show 3 more comments

I'm implementing a program in FreePascal in Win10(64-bit). The problem state:

'Given a string, replace all substring 'child' with 'childhood' '

'Replace all 'child' with 'childhood''

I try this program

uses crt;

var s, newS : string;

    tmp, tmp2, tmp3 : int64;

    tmpstr, tmpstr2 : string;

    step, step2, step3 : longint;

    position : longint;



begin

        clrscr;

        write('Nhap xau : '); readln(s);

        //main mechanism



        while pos('child',s) <> 0 do begin

                position := pos('child', s);

                delete(s, pos('child',1), 5);

                insert('childhood',s,position);

                inc(position, 9);

                newS := '';

                for step:=position to length(s) do begin

                        newS := newS + s[step];

                end;

                s := newS;

        end;

        writeln(s);



        readkey;

end.

You can see that this part:

inc(position, 9);

newS := '';

for step:=position to length(s) do begin

        newS := newS + s[step];

end;

s := newS;

was used to try to cut off the while loop, but it doesn't work. Any idea?

Thanks a lot and have a good day! Thanks for reading this question thread! =)

asked Nov 23 '18 at 14:55

hungnguyen

378

1

Given the requirement is as you've stated, I suggest replacing your program with a call to StringReplace.

– Sertac Akyuz
Nov 23 '18 at 15:17

This is homework I guess. What your instructor is hoping is that you will debug your program to find out what is going wrong. Do you know how to debug? If not, there is no time like the present.

– David Heffernan
Nov 23 '18 at 15:20

1

I hope you are aware of the fact that the replacement 'childhood' contains the search text, 'child' and that this should have consequences for how and where you try to find your search text after you replaced it. Otherwise 'child' will become 'childhood', 'childhoodhood', 'childhoodhoodhood', etc. ad infinitum. So do as @David says, and debug your program. It is an important skill and easy to learn.

– Rudy Velthuis
Nov 23 '18 at 19:29

FWIW, since the line delete(s, pos('child',1), 5);probably doesn't compile at all, it looks as if this is not exactly your code. Please always post the exact code (copy and paste) that gives you problems. Do not type it from memory or from view. Use copy and paste. How can we tell what is wrong with your code if we don't even see your exact code? The error could just as well be in the in the part you typed wrongly.

– Rudy Velthuis
Nov 23 '18 at 19:33

@Rudy_Velthius this is my exact code. I copy paste from notepad

– hungnguyen
Nov 24 '18 at 2:54

|
show 3 more comments

I'm implementing a program in FreePascal in Win10(64-bit). The problem state:

'Given a string, replace all substring 'child' with 'childhood' '

'Replace all 'child' with 'childhood''

I try this program

uses crt;

var s, newS : string;

    tmp, tmp2, tmp3 : int64;

    tmpstr, tmpstr2 : string;

    step, step2, step3 : longint;

    position : longint;



begin

        clrscr;

        write('Nhap xau : '); readln(s);

        //main mechanism



        while pos('child',s) <> 0 do begin

                position := pos('child', s);

                delete(s, pos('child',1), 5);

                insert('childhood',s,position);

                inc(position, 9);

                newS := '';

                for step:=position to length(s) do begin

                        newS := newS + s[step];

                end;

                s := newS;

        end;

        writeln(s);



        readkey;

end.

You can see that this part:

inc(position, 9);

newS := '';

for step:=position to length(s) do begin

        newS := newS + s[step];

end;

s := newS;

was used to try to cut off the while loop, but it doesn't work. Any idea?

Thanks a lot and have a good day! Thanks for reading this question thread! =)

asked Nov 23 '18 at 14:55

hungnguyen

378

I'm implementing a program in FreePascal in Win10(64-bit). The problem state:

'Given a string, replace all substring 'child' with 'childhood' '

'Replace all 'child' with 'childhood''

I try this program

uses crt;

var s, newS : string;

    tmp, tmp2, tmp3 : int64;

    tmpstr, tmpstr2 : string;

    step, step2, step3 : longint;

    position : longint;



begin

        clrscr;

        write('Nhap xau : '); readln(s);

        //main mechanism



        while pos('child',s) <> 0 do begin

                position := pos('child', s);

                delete(s, pos('child',1), 5);

                insert('childhood',s,position);

                inc(position, 9);

                newS := '';

                for step:=position to length(s) do begin

                        newS := newS + s[step];

                end;

                s := newS;

        end;

        writeln(s);



        readkey;

end.

You can see that this part:

inc(position, 9);

newS := '';

for step:=position to length(s) do begin

        newS := newS + s[step];

end;

s := newS;

was used to try to cut off the while loop, but it doesn't work. Any idea?

Thanks a lot and have a good day! Thanks for reading this question thread! =)

infinite-loop freepascal

asked Nov 23 '18 at 14:55

hungnguyen

378

asked Nov 23 '18 at 14:55

hungnguyen

378

asked Nov 23 '18 at 14:55

hungnguyen

378

asked Nov 23 '18 at 14:55

hungnguyen

378

asked Nov 23 '18 at 14:55

hungnguyen

378

1

Given the requirement is as you've stated, I suggest replacing your program with a call to StringReplace.

– Sertac Akyuz
Nov 23 '18 at 15:17

This is homework I guess. What your instructor is hoping is that you will debug your program to find out what is going wrong. Do you know how to debug? If not, there is no time like the present.

– David Heffernan
Nov 23 '18 at 15:20

1

I hope you are aware of the fact that the replacement 'childhood' contains the search text, 'child' and that this should have consequences for how and where you try to find your search text after you replaced it. Otherwise 'child' will become 'childhood', 'childhoodhood', 'childhoodhoodhood', etc. ad infinitum. So do as @David says, and debug your program. It is an important skill and easy to learn.

– Rudy Velthuis
Nov 23 '18 at 19:29

FWIW, since the line delete(s, pos('child',1), 5);probably doesn't compile at all, it looks as if this is not exactly your code. Please always post the exact code (copy and paste) that gives you problems. Do not type it from memory or from view. Use copy and paste. How can we tell what is wrong with your code if we don't even see your exact code? The error could just as well be in the in the part you typed wrongly.

– Rudy Velthuis
Nov 23 '18 at 19:33

@Rudy_Velthius this is my exact code. I copy paste from notepad

– hungnguyen
Nov 24 '18 at 2:54

|
show 3 more comments

1

Given the requirement is as you've stated, I suggest replacing your program with a call to StringReplace.

– Sertac Akyuz
Nov 23 '18 at 15:17

This is homework I guess. What your instructor is hoping is that you will debug your program to find out what is going wrong. Do you know how to debug? If not, there is no time like the present.

– David Heffernan
Nov 23 '18 at 15:20

1

I hope you are aware of the fact that the replacement 'childhood' contains the search text, 'child' and that this should have consequences for how and where you try to find your search text after you replaced it. Otherwise 'child' will become 'childhood', 'childhoodhood', 'childhoodhoodhood', etc. ad infinitum. So do as @David says, and debug your program. It is an important skill and easy to learn.

– Rudy Velthuis
Nov 23 '18 at 19:29

FWIW, since the line delete(s, pos('child',1), 5);probably doesn't compile at all, it looks as if this is not exactly your code. Please always post the exact code (copy and paste) that gives you problems. Do not type it from memory or from view. Use copy and paste. How can we tell what is wrong with your code if we don't even see your exact code? The error could just as well be in the in the part you typed wrongly.

– Rudy Velthuis
Nov 23 '18 at 19:33

@Rudy_Velthius this is my exact code. I copy paste from notepad

– hungnguyen
Nov 24 '18 at 2:54

Given the requirement is as you've stated, I suggest replacing your program with a call to StringReplace.

– Sertac Akyuz
Nov 23 '18 at 15:17

This is homework I guess. What your instructor is hoping is that you will debug your program to find out what is going wrong. Do you know how to debug? If not, there is no time like the present.

– David Heffernan
Nov 23 '18 at 15:20

I hope you are aware of the fact that the replacement 'childhood' contains the search text, 'child' and that this should have consequences for how and where you try to find your search text after you replaced it. Otherwise 'child' will become 'childhood', 'childhoodhood', 'childhoodhoodhood', etc. ad infinitum. So do as @David says, and debug your program. It is an important skill and easy to learn.

– Rudy Velthuis
Nov 23 '18 at 19:29

FWIW, since the line delete(s, pos('child',1), 5);probably doesn't compile at all, it looks as if this is not exactly your code. Please always post the exact code (copy and paste) that gives you problems. Do not type it from memory or from view. Use copy and paste. How can we tell what is wrong with your code if we don't even see your exact code? The error could just as well be in the in the part you typed wrongly.

– Rudy Velthuis
Nov 23 '18 at 19:33

@Rudy_Velthius this is my exact code. I copy paste from notepad

– hungnguyen
Nov 24 '18 at 2:54

|
show 3 more comments

1 Answer
1

active

oldest

votes

This is just one of the possibilities, not optimized but perhaps the easiest to understand:

oldstr := 'original child string';

newstr := '';



while oldstr<>'' do begin

  // analyze the string from left to right

  if copy(oldstr, 1 5)='child' then begin

    // match found, perform substitution

    newstr := newstr+'childhood';

    delete(oldstr, 1, 5)

  end else begin

    // does not match, go ahead to the next possibility

    newstr := newstr+oldstr[1];

    delete(oldstr, 1, 1)

  end

end

// now newstr is the desired result

The gotcha here was to not analyze again what was added in a previous step (child->childhood). The algorithm above (warning, I've not tested it) ensures that any single char from the original string is checked only once.

answered Dec 23 '18 at 10:43

linuxfan

2,0982720

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

This is just one of the possibilities, not optimized but perhaps the easiest to understand:

oldstr := 'original child string';

newstr := '';



while oldstr<>'' do begin

  // analyze the string from left to right

  if copy(oldstr, 1 5)='child' then begin

    // match found, perform substitution

    newstr := newstr+'childhood';

    delete(oldstr, 1, 5)

  end else begin

    // does not match, go ahead to the next possibility

    newstr := newstr+oldstr[1];

    delete(oldstr, 1, 1)

  end

end

// now newstr is the desired result

answered Dec 23 '18 at 10:43

linuxfan

2,0982720

add a comment |

This is just one of the possibilities, not optimized but perhaps the easiest to understand:

oldstr := 'original child string';

newstr := '';



while oldstr<>'' do begin

  // analyze the string from left to right

  if copy(oldstr, 1 5)='child' then begin

    // match found, perform substitution

    newstr := newstr+'childhood';

    delete(oldstr, 1, 5)

  end else begin

    // does not match, go ahead to the next possibility

    newstr := newstr+oldstr[1];

    delete(oldstr, 1, 1)

  end

end

// now newstr is the desired result

answered Dec 23 '18 at 10:43

linuxfan

2,0982720

add a comment |

This is just one of the possibilities, not optimized but perhaps the easiest to understand:

oldstr := 'original child string';

newstr := '';



while oldstr<>'' do begin

  // analyze the string from left to right

  if copy(oldstr, 1 5)='child' then begin

    // match found, perform substitution

    newstr := newstr+'childhood';

    delete(oldstr, 1, 5)

  end else begin

    // does not match, go ahead to the next possibility

    newstr := newstr+oldstr[1];

    delete(oldstr, 1, 1)

  end

end

// now newstr is the desired result

answered Dec 23 '18 at 10:43

linuxfan

2,0982720

This is just one of the possibilities, not optimized but perhaps the easiest to understand:

oldstr := 'original child string';

newstr := '';



while oldstr<>'' do begin

  // analyze the string from left to right

  if copy(oldstr, 1 5)='child' then begin

    // match found, perform substitution

    newstr := newstr+'childhood';

    delete(oldstr, 1, 5)

  end else begin

    // does not match, go ahead to the next possibility

    newstr := newstr+oldstr[1];

    delete(oldstr, 1, 1)

  end

end

// now newstr is the desired result

answered Dec 23 '18 at 10:43

linuxfan

2,0982720

answered Dec 23 '18 at 10:43

linuxfan

2,0982720

answered Dec 23 '18 at 10:43

linuxfan

2,0982720

answered Dec 23 '18 at 10:43

linuxfan

2,0982720

add a comment |

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