Perl srand()用法及代碼示例

Perl中的srand()函數可幫助rand()函數在每次運行程序時生成一個恒定值。
每次調用rand()函數以獲取恒定的隨機值時，此srand()函數使用相同的參數。

用法： srand(seed)

參數：
seed :它是一個整數值。

返回：該函數不返回任何值。

示例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");

輸出：

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：在上麵的代碼中，可以看出srand()函數的參數是相同的，這就是為什麽rand()函數每次調用時都產生相同的隨機值的原因。

示例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");

輸出：

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：在上麵的代碼中，可以看出srand()函數具有不同的參數，這就是為什麽rand()函數每次調用時都會產生不同的隨機值的原因。

示例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");

輸出：

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：在上麵的代碼中，可以看出未使用srand()函數，這就是為什麽rand()函數每次調用時都會產生不同的隨機值的原因。

相關用法

注：本文由純淨天空篩選整理自Kanchan_Ray大神的英文原創作品 Perl | srand() Function。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。