Pascal编译报错：类型不兼容，期望LongInt却得到Boolean求排查

报错信息 #

convertNumbers.pas(21,14) Error: Incompatible types: got "Boolean" expected "LongInt"
convertNumbers.pas(42,4) Fatal: There were 1 errors compiling module, stopping

问题根源 #

错误出在Dual2Dec过程的WHILE循环条件行：

WHILE iCount < 16 AND iDecimal > 0 DO

Pascal中位运算符AND的优先级高于比较运算符<和>，编译器会将上述表达式错误解析为：

WHILE (iCount < (16 AND iDecimal)) > 0 DO

这里16 AND iDecimal是整数位运算，结果为长整型；iCount < 长整型得到布尔值，随后用这个布尔值和整数0比较，就触发了「布尔值与长整型不兼容」的编译错误。

修复方案 #

给两个比较表达式分别加上括号，明确逻辑运算的顺序：

WHILE (iCount < 16) AND (iDecimal > 0) DO

修复后的完整代码 #

PROGRAM convertNumbers;

TYPE
  aDual = ARRAY[0..15] OF BOOLEAN;

PROCEDURE Dual2Dec (iDecimal: INTEGER; VAR aDualCalc: aDual);
VAR
  iCount: INTEGER;
  bDivision: BOOLEAN;
  iCalculation: INTEGER;

BEGIN
  iCount := 0;    

  WHILE (iCount < 16) AND (iDecimal > 0) DO
  BEGIN
    iCalculation := iDecimal mod 2;
    IF iCalculation = 0 THEN
      bDivision := FALSE
    ELSE
      bDivision := TRUE;
    aDualCalc[iCount] := bDivision;
    iDecimal := iDecimal div 2;
    iCount := iCount + 1;
  END;
END;

BEGIN

END.

内容的提问来源于stack exchange，提问作者Slan