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Perl | srand()函数

原文:https://www.geeksforgeeks.org/perl-srand-function/

Perl 中的 srand()函数帮助 rand()函数在每次程序运行时生成一个常量值。 每次调用 rand()函数获取恒定的随机值时，该 srand()函数使用相同的参数。

语法: srand(种子)

参数: 种子:为整数值。

返回:该函数不返回值。

例 1:

#!/usr/bin/perl

# Calling the srand() function and 
# Printing a random value 
srand(5);
print("The first random number is ", rand(), ".\n");

# Calling the srand() function and 
# Printing a random value 
srand(5);
print("The second random number is ", rand(), ".\n");

# Calling the srand() function and 
# Printing a random value 
srand(5);
print("The third random number is ", rand(), ".\n");

# Calling the srand() function and 
# Printing a random value 
srand(5);
print("The fourth random number is ", rand(), ".\n");

输出:

The first random number is 0.524839579434232.
The second random number is 0.524839579434232.
The third random number is 0.524839579434232.
The fourth random number is 0.524839579434232.

注意:在上面的代码中，可以看到 srand()函数的参数是相同的，这就是为什么每次调用 rand()函数都会产生相同的随机值。

例 2:

#!/usr/bin/perl

# Calling the srand() function and 
# Printing a random value 
srand(5);
print("The first random number is ", rand(), ".\n");

# Calling the srand() function and 
# Printing a random value 
srand(6);
print("The second random number is ", rand(), ".\n");

# Calling the srand() function and 
# Printing a random value 
srand(7);
print("The third random number is ", rand(), ".\n");

# Calling the srand() function and 
# Printing a random value 
srand(8);
print("The fourth random number is ", rand(), ".\n");

输出:

The first random number is 0.524839579434232.
The second random number is 0.395641888099821.
The third random number is 0.266444196765409.
The fourth random number is 0.137246505430998.

注意:在上面的代码中，可以看到 srand()函数具有不同的参数，这就是为什么每次调用 rand()函数都会产生不同的随机值。

例 3:

#!/usr/bin/perl

# Printing a random value without calling the srand() function
print("The first random number is ", rand(), ".\n");

# Printing a random value without calling the srand() function
print("The second random number is ", rand(), ".\n");

# Printing a random value without calling the srand() function
print("The third random number is ", rand(), ".\n");

# Printing a random value without calling the srand() function
print("The fourth random number is ", rand(), ".\n");

输出:

The first random number is 0.241482914266275.
The second random number is 0.821264154368208.
The third random number is 0.870625858233449.
The fourth random number is 0.012084407123389.

注意:在上面的代码中，可以看到没有使用 srand()函数，这就是为什么每次调用 rand()函数都会产生不同的随机值。

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