ISO Pascal reference manual

PROGRAM fail;
VAR n : integer;
FUNCTION one:integer;
BEGIN
one := 1; [correct}
END;
BEGIN
n := one; (correct}
one := 1; (incorrect - not inside 'one'}
END.
*ERROR 135 -- function cannot be used in this way
Appendix A
This message is issued when a required function is used as though it were a
variable.
PROGRAM fail;
BEGIN
sqrt := 0;
END.
*ERROR 136 -- the type of the array index does not match the type
given in the array declaration
The expression used to select an element of an array must give a value
which is of the same type as was used to declare the array.
PROGRAM fail(output);
TYPE person = (fred, fill, anne, jim);
VAR who : person;
lucky : ARRAY [person] of Boolean;
BEGIN
IF lucky[who] THEN writeln('yes')
(OK - who is 'person'-type}
IF lucky[true] THEN writeln('no')
[wrong - true is not 'person'-type}
END.
Pascal Issue I 93