Установите корректность использования условного оператора в следующих ситуациях. if x<0 then x:=-y; if x>0 x:=y; if x>0 else x:=y; if x<0; then x:=-y;

1. Breakdown the Problem

We need to analyze the correctness of using the conditional operator in each of the provided situations.

2. Relevant Concepts

Conditional structures typically follow a syntax that varies slightly by programming language, but common elements include:

• A condition followed by an action if the condition is true.
• The use of if, then, and else keywords.
• Proper use of punctuation such as semicolons and colons.

3. Analysis and Detail

1. if x<0 then x:=-y;

   • This is syntactically correct. It checks if $x$ is less than 0 and assigns $-y$ to $x$ if the condition is true.

2. if x>0 x:=y;

   • This is incorrect because it lacks the then keyword. The correct form should be if x > 0 then x := y;.

3. if x>0 else x:=y;

   • This is incorrect because there is no then part for the if. It should be structured as if x > 0 then ... else ....

4. if x<0; then x:=-y;

   • This is incorrect because of the unnecessary semicolon right after the condition. The correct form should be if x < 0 then x := -y;.

4. Verify and Summarize

• The first statement is correct.
• The second, third, and fourth statements are incorrect due to syntax issues.

Final Answer

1. Correct: if x<0 then x:=-y;
2. Incorrect: if x>0 x:=y; (missing then)
3. Incorrect: if x>0 else x:=y; (missing then)
4. Incorrect: if x<0; then x:=-y; (unnecessary semicolon)