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94 lines
2.5 KiB
Markdown
94 lines
2.5 KiB
Markdown
# mers
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Mers is a high-level programming language.
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It is designed to be safe (it doesn't crash at runtime) and as simple as possible.
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Install from *crates.io*:
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```sh
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cargo install mers
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```
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See also:
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[Quickstart](Quickstart.md)
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## what makes it special
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### Simplicity
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Mers is simple. There are only few expressions:
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- Values (`1`, `"my string"`, ...)
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- Blocks (`{}`)
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- Tuples (`()`) and Objects (`{}`)
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- Assignments (`=`)
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- Variable initializations (`:=`)
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- Variables (`my_var`, `&my_var`)
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- If statements (`if <condition> <then> [else <else>]`)
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- Functions (`arg -> <do something>`)
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- Function calls `arg.function` or `arg1.function(arg2, arg3)` (= `(arg1, arg2, arg3).function`)
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Everything else is implemented as a function.
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### Types and Safety
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Mers is built around a type-system where a value could be one of multiple types.
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```
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x := if condition { 12 } else { "something went wrong" }
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```
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In mers, the compiler tracks all the types in your program,
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and it will catch every possible crash before the program even runs:
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If we tried to use `x` as an int, the compiler would complain since it might be a string, so this **does not compile**:
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```
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list := (1, 2, if true 3 else "not an int")
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list.sum.println
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```
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Type-safety for functions is different from what you might expect.
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You don't need to tell mers what type your function's argument has - you just use it however you want as if mers was a dynamically typed language:
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```
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sum_doubled := iter -> {
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one := iter.sum
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(one, one).sum
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}
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(1, 2, 3).sum_doubled.println
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```
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We could try to use the function improperly by passing a string instead of an int:
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```
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(1, 2, "3").sum_doubled.println
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```
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But mers will catch this and show an error, because the call to `sum` inside of `sum_doubled` would fail.
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### Error Handling
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Errors in mers are normal values.
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For example, `("ls", ("/")).run_command` has the return type `({Int/()}, String, String)/RunCommandError`.
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This means it either returns the result of the command (exit code, stdout, stderr) or an error (a value of type `RunCommandError`).
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So, if we want to print the programs stdout, we could try
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```
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(s, stdout, stderr) := ("ls", ("/")).run_command
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stdout.println
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```
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But if we encountered a `RunCommandError`, mers wouldn't be able to assign the value to `(s, stdout, stderr)`, so this doesn't compile.
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Instead, we need to handle the error case, using the `try` function:
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```
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("ls", ("/")).run_command.try((
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(s, stdout, stderr) -> stdout.println,
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error -> error.println,
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))
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```
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## docs
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docs will be available in some time. for now, check mers_lib/src/program/configs/*
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