I get this error on my insertion sort algorithm:
insertionsort.lpr(19,17) Error: Incompatible types: got "Boolean" expected "LongInt"
Here's the line 19 of my code
while j > 0 and A[j]>key do
I have tried googling all over the internet but i couldn't find any syntax errors or anything.
Here's the full code if it helps :
program instert;
uses crt;
const
N = 5;
var
i:integer;
j:integer;
key:integer;
A : Array[1..N] of Integer;
procedure insertionsort;
begin
for i := 2 to N do
begin
key := A[1];
j:= i - 1;
while j > 0 and A[j]>key do
begin
A[j+1] := A[j] ;
j := j-1;
end;
A[j+1] := key ;
end;
end;
begin
A[1]:= 9;
A[2]:= 6;
A[3]:= 7;
A[4]:= 1;
A[5]:= 2;
insertionsort;
end.
I also get the same error on the bubble sort algorithm i did. Here's the error line
bubblesort.lpr(26,14) Error: Incompatible types: got "Boolean" expected "LongInt"
Here's line 26 of my algorithm:
until flag = false or N = 1 ;
Here's the full code:
program bubblesort;
uses crt;
var
flag:boolean;
count:integer;
temp:integer;
N:integer;
A : Array[1..N] of Integer;
procedure bubblesort ;
begin
Repeat
flag:=false;
for count:=1 to (N-1) do
begin
if A[count] > A[count + 1] then
begin
temp := A[count];
A[count] := A[count + 1];
A[count] := temp;
flag := true;
end;
end;
N := N - 1;
until flag = false or N = 1 ;
end;
begin
A[1]:= 9;
A[2]:= 6;
A[3]:= 7;
A[4]:= 1;
A[5]:= 2;
N := 5;
bubblesort;
end.
In Pascal, boolean operators and
and or
have higher precedence than the comparison operators >
, =
, etc. So in the expression:
while j > 0 and A[j] > key do
Given that and
has higher precedence, Pascal sees this as:
while (j > (0 and A[j])) > key do
0 and A[j]
are evaluated as a bitwise and
(since the arguments are integers) resulting in an integer. Then the comparison, j > (0 and A[j])
is evaluated as a boolean result, leaving a check of that with > key
, which is boolean > longint
. You then get the error that a longint
is expected instead of the boolean
for the arithmetic comparison.
The way to fix it is to parenthesize:
while (j > 0) and (A[j] > key) do ...
The same issue applies with this statement:
until flag = false or N = 1 ;
which yields an error because or
is higher precedence than =
. So you can parenthesize:
until (flag = false) or (N = 1);
Or, more canonical for booleans:
until not flag or (N = 1); // NOTE: 'not' is higher precedence than 'or'
When in doubt about the precedence of operators, parenthesizing is a good idea, as it removes the doubt about what order operations are going to occur.