try-catch
try
可能出错的程序
catch 异常类型变量名
异常处理程序
finally
无论如何最后都要执行的程序
end
x = [2, -2, "a"]
for xi in x
try
y = sqrt(xi)
println("√", xi, " = ", y)
catch e
if isa(e, DomainError)
println("√", xi, ": 平方根函数定义域异常")
else
print("√", xi, ": 平方根函数其它异常")
end
end
end
## √2 = 1.4142135623730951
## √-2: 平方根函数定义域异常
## √a: 平方根函数其它异常
try finally
f = open("file")
try
# operate on file f
finally
close(f)
end
throw
#利用短路逻辑，如果k<0就执行后边的语句 抛出错误
k = -1
k > 0 || throw(ArgumentError("k must be non-negtive")
@assert
k = -1
@assert k > 0 "k must be non-negtive"
@assert(k > 0, "k must be non-negtive")
# @assert相当于
if k > 0
nothing
else
Base.throw(Base.AssertionError("k must be non-negtive"))
end
error
平方根函数，如果参数x<0，则报错"negative x not allowed"
fussy_sqrt(x) = x >= 0 ? sqrt(x) : error("negative x not allowed")
Julia is a high-level, dynamic programming language. Its features are well suited for numerical analysis and computational science. Distinctive aspects of Julia's design include a type system with parametric polymorphism in a dynamic programming language; with multiple dispatch as its core programming paradigm.The most significant departures of Julia from typical dynamic languages are:The core language imposes very little; Julia Base and the standard library are written in Julia itself, including primitive operations like integer arithmetic.A rich language of types for constructing and describing objects, that can also optionally be used to make type declarations.The ability to define function behavior across many combinations of argument types via multiple dispatch.Automatic generation of efficient, specialized code for different argument types.Good performance, approaching that of statically-compiled languages like C.
