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Diffstat (limited to 'src/content/chapter5_advance_features/lesson04_externals')
-rw-r--r-- | src/content/chapter5_advance_features/lesson04_externals/code.gleam | 17 | ||||
-rw-r--r-- | src/content/chapter5_advance_features/lesson04_externals/text.html | 25 |
2 files changed, 0 insertions, 42 deletions
diff --git a/src/content/chapter5_advance_features/lesson04_externals/code.gleam b/src/content/chapter5_advance_features/lesson04_externals/code.gleam deleted file mode 100644 index ade2c54..0000000 --- a/src/content/chapter5_advance_features/lesson04_externals/code.gleam +++ /dev/null @@ -1,17 +0,0 @@ -import gleam/io - -// A type with no Gleam constructors -pub type DateTime - -// An external function that creates an instance of the type -@external(javascript, "./my_package_ffi.mjs", "now") -pub fn now() -> DateTime - -// The `now` function in `./my_package_ffi.mjs` looks like this: -// external function now() { -// return new Date(); -// } - -pub fn main() { - io.debug(now()) -} diff --git a/src/content/chapter5_advance_features/lesson04_externals/text.html b/src/content/chapter5_advance_features/lesson04_externals/text.html deleted file mode 100644 index 81202d6..0000000 --- a/src/content/chapter5_advance_features/lesson04_externals/text.html +++ /dev/null @@ -1,25 +0,0 @@ -<p> - Sometimes in our projects we want to use code written in other languages, most - commonly Erlang and JavaScript, depending on which runtime is being used. - Gleam's <em>external functions</em> and <em>external types</em> allow us to - import and use this non-Gleam code. -</p> -<p> - An external type is a one that has no constructors. Gleam doesn't know what - shape it has or how to create one, it only knows that it exists. -</p> -<p> - An external function is one that has the <code>@external</code> attribute on - it, directing the compiler to use the specified module function as the - implementation, instead of Gleam code. -</p> -<p> - The compiler can't tell the types of functions written in other languages, so - when the external attribute is given type annotations must be provided. Gleam - trusts that the type given is correct so an inaccurate type annotation can - result in unexpected behaviour and crashes at runtime. Be careful! -</p> -<p> - External functions are useful but should be used sparingly. Prefer to write - Gleam code where possible. -</p> |