在 Julia 中获取集合的第一个索引 – firstindex() 方法

firstindex()是 julia 中的一个内置函数，用于返回指定集合的第一个索引。如果给出了维度d ，则返回沿维度 d 的集合的第一个索引。

Syntax:
firstindex(collection)
or
firstindex(collection, d)

Parameters:

• collection: Specified collection.
• b: Specified dimension.

Returns: It returns the first index of the specified collection. If a dimension d is given, return the first index of collection along dimension d.

示例 1：

# Julia program to illustrate 
# the use of firstindex() method
   
# Getting the first index of the specified collection.
println(firstindex(0))
println(firstindex([1, 2, 3]))
println(firstindex([2 4; 5 6]))
println(firstindex([3; 5; 7; 9]))

输出：

示例 2：

# Julia program to illustrate 
# the use of firstindex() method
   
# Getting the first index of the specified 
# collection. If a dimension d is given, 
# return the first index of collection 
# along dimension d.
println(firstindex(rand(1, 2, 3, 4), 1))
println(firstindex(rand(1, 2, 3, 4), 2))
println(firstindex([1, 2, 3], 2))
println(firstindex([2 4; 6 8], 2))
println(firstindex([2; 4; 6; 8], 2))
println(firstindex(cat([1 2; 3 4], [5 6; 7 8], [2 2; 3 4], dims = 3);))

输出：