hla - 为什么在语句 maxVal=input 中需要“（”而不是“=”

Question

program MaxMin;

#include("stdlib.hhf")

static

    count: int32:=0;
    input: int32;
    maxVal: int32;
    minVal: int32;
    sum: int32:=0;
    boolVar : boolean:= true;

begin MaxMin;


while(boolVar) do

    stdout.put("Enter a number, 0 to stop:");
    stdin.get(input);
    
    if(input==0)then
        break;
    elseif(count == 0)then
        maxVal=input;
        minVal=input;
    elseif(input>maxVal)then
        maxVal=input;
    elseif(input<minVal)then
        minVal=input;
    endif;
    
    add(input,sum);
    add(1,count);
    
    
endwhile;

stdout.newln();

stdout.put("Total: ",sum,nl,"Count: ",count,nl,"Maximum: ",maxVal,nl,"Minimum: ",minVal,nl);


end MaxMin;

Answer 1

环境

• HLA（高级汇编器 - HLABE 后端，LD 链接器）版本 2.16 build 4409（原型）
• Ubuntu 20.04.1

解决方案

• 问题是maxVal=input;HLA 中的语句无效。要纠正这个问题，我们的mov说明如下：mov(input, maxVal);。
• 但是，在此更正之后，您将看到以下错误：

Assembling "src.hla" to "src.o"
Error in file "src.hla" at line 27 [errid:102032/hlaparse.bsn]:
Memory to memory comparisons are illegal.
Near: << ) >>

hlaparse: oututils.c:2480: FreeOperand: Assertion `o->l.leftOperand != ((void *)0)' failed.
Aborted (core dumped)

• 这是因为 HLA 不支持内存对象之间的比较。一种解决方案是将用户输入的数字存储在其中EAX并将所有出现的input变量更改为EAX。

例子

program MaxMin;
#include("stdlib.hhf")

storage
    maxVal: int32; 
    minVal: int32;

static
    count:   int32:=   0;
    sum:     int32:=   0;
    boolVar: boolean:= true;

begin MaxMin;
    while(boolVar) do
        stdout.put("Enter a number, 0 to stop: ");
        stdin.geti32();

        if (EAX = 0 ) then
            break;
        elseif ( count = 0 ) then
            mov(EAX, maxVal);
            mov(EAX, minVal);
        elseif (EAX > maxVal) then
            mov(EAX, maxVal);
        elseif (EAX < minVal) then
            mov(EAX, minVal);
        endif;
    
        add(EAX, sum);
        add(1, count);   
    endwhile;

    stdout.newln();
    stdout.put("Total: ",sum,nl,"Count: ",count,nl,"Maximum: ",maxVal,nl,"Minimum: ",minVal,nl);
end MaxMin;