作为一个更加具体的例子，一个范用的方阵乘法的伪代码是： function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = t calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well C API 也就能够进行更多语言的桥接。(例如在 Python 或是 C# 中 调用 Julia ). 28.1 高级别嵌入 Note: 本节包含可运行在类 Unix 系统上的、使用 C 编写的嵌入式 Julia 代码。Windows 平台请参阅下 一节。 我们从一个简单的 C 程序开始初始化 Julia 并调用一些 Julia 代码： #include JULIA_DEFINE_FAST_TLS()

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = ty `+` calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well Default is 0755 or 0644, de- pending on the blob. 913 914 CHAPTER 79. LIBGIT2 • file_open_flags: bi�lags used to open any files during the checkout. • notify_flags: Flags for what sort of conflicts

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = ty `+` calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well Default is 0755 or 0644, de- pending on the blob. 885 886 CHAPTER 77. LIBGIT2 • file_open_flags: bi�lags used to open any files during the checkout. • notify_flags: Flags for what sort of conflicts

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = ty `+` calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well Default is 0755 or 0644, de- pending on the blob. 883 884 CHAPTER 77. LIBGIT2 • file_open_flags: bi�lags used to open any files during the checkout. • notify_flags: Flags for what sort of conflicts

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = ty `+` calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well Default is 0755 or 0644, de- pending on the blob. 915 916 CHAPTER 80. LIBGIT2 • file_open_flags: bi�lags used to open any files during the checkout. • notify_flags: Flags for what sort of conflicts

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = ty `+` calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well Default is 0755 or 0644, de- pending on the blob. 923 924 CHAPTER 82. LIBGIT2 • file_open_flags: bi�lags used to open any files during the checkout. • notify_flags: Flags for what sort of conflicts

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = ty `+` calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well Default is 0755 or 0644, de- pending on the blob. 921 922 CHAPTER 81. LIBGIT2 • file_open_flags: bi�lags used to open any files during the checkout. • notify_flags: Flags for what sort of conflicts

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = t calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well similar(::SpecialSparseMatrix, ::Type, ::Dims) returns a dense zero matrix. As a consequence, products of bi-, tri- and symmetric tridiagonal matrices with each other result in dense output. Moreover, constructing

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = t calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well similar(::SpecialSparseMatrix, ::Type, ::Dims) returns a dense zero matrix. As a consequence, products of bi-, tri- and symmetric tridiagonal matrices with each other result in dense output. Moreover, constructing

pseudo-code might look like: function matmul(a::AbstractMatrix, b::AbstractMatrix) op = (ai, bi) -> ai * bi + ai * bi ## this is insufficient because it assumes `one(eltype(a))` is constructable: # R = t calls `promote_type` ## but this is not true for some types, such as Bool: # R = promote_type(ai, bi) # this is wrong, since depending on the return value # of type-inference is very brittle (as well similar(::SpecialSparseMatrix, ::Type, ::Dims) returns a dense zero matrix. As a consequence, products of bi-, tri- and symmetric tridiagonal matrices with each other result in dense output. Moreover, constructing