Riml is a subset of VimL with some nice added features. It compiles to plain VimL.
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README.md

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Riml, a relaxed VimL

Riml is a subset of VimL with some added features, and it compiles to plain VimL. Some of the added features include classes, string interpolation, heredocs, default case-sensitive string comparison, default parameters in functions, and other things programmers tend to take for granted. To see how Riml is compiled to VimL, just take a look at this README. The left side is Riml, and the right side is the VimL after compilation.

Variables

count = 1                     let s:count = 1
while count < 5               while s:count < 5
  source other.vim              source other.vim
  count += 1                    let s:count += 1
end                           endwhile

If you don't specify a scope modifier (or 'namespace' in Vimspeak), it's script local (s:) by default in the global scope. Within a function, variables without scope modifiers are plain old local variables.

###globally

a = 3                         let s:a = 3

###locally (within function or for loop)

def exampleFunc(msg)          function! s:exampleFunc(msg)
  a = 3                         let a = 3
  echo msg                      echo a:msg
end                           endfunction

for i in expr()               for i in s:expr()
  echo i                        echo i
end                           endfor

Notice that within a function, it's unnecessary to prefix argument variables with 'a:'. This is, of course, unless we shadow the argument variable by creating our own local variable called 'msg'. In that case, we'd have to refer to the argument variable as 'a:msg' explicitly. Shadowing variables in Riml is considered bad practice, as it's much easier to just come up with unique variable names across a scope.

###Assignment as Expression

let a = b = c = 0                   let s:c = 0
                                    let s:b = s:c
                                    let s:a = s:b

The 'let' is optional in Riml for all assignments. Without it, the results are the same.

###Multiple Assignment Statement

a = 0, b = 1                        let s:a = 0
                                    let s:b = 1

###Checking for existence

unless callcount?                     if !exists("s:callcount")
  callcount = 0                        let s:callcount = 0
end                                   endif
callcount += 1                        let s:callcount += 1
echo "called #{callcount} times"      echo "called " . s:callcount . " times"

Notice in the last line of Riml there's string interpolation. This works in double-quoted strings and heredocs, which we'll encounter later.

In Riml, you can choose to end any block with 'end', or with whatever you used to do in VimL ('endif', 'endfunction', etc...). Also, 'if' and 'unless' can now be used as statement modifiers:

callcount = 0 unless callcount?
callcount += 1
echo "called #{callcount} times"

Here, the compiled output is the same as the previous example's. Both 'if' and 'unless' can be used this way.

###True and False

a = true                                      let s:a = 1
b = false                                     let s:b = 0

Operators And Case Sensitivity

if "hi" == greeting                           if "hi" ==# s:greeting
  echo greeting                                 echo s:greeting
end                                           end

Comparisons compile to case-sensitive by default. To get case-insensitive comparisons, you have to explicitly use the form ending in '?' (ex: '==?'). The only operators that don't add a '#' even though the forms exist are the 'is' and 'isnot' operators. This is because 'is' is much different from its cousin 'is#', and the same is true of 'isnot'.

###=== Operator

Oh no, not another of those operators! Well, this one is pretty sweet actually. In VimL, automatic type conversion can be a pain. For example:

echo 4 ==# "4"
=> 1

To mitigate this, we can wrap each side in a list, since lists are more strict regarding equality:

echo [4] ==# ["4"]
=> 0

The '===' operator wraps both operands in lists:

echo 4 === "4"                        echo [4] ==# ["4"]
=> 0

Heredocs

msg = <<EOS                           let s:msg = "a vim heredoc! " . s:cryForJoy() . "!\nHooray!"
A vim heredoc! #{cryForJoy()}!
Hooray!
EOS

Riml heredocs must have the ending pattern ('EOS' in this case, but can be anything) start at the beginning of the line. Interpolated expressions are allowed in heredocs.

Functions

def fillSearchPat             function! s:fillSearchPat()
  @/ = getSearchPat()           let @/ = s:getSearchPat()
  return @/                     return @/
end                           endfunction

Functions are by default prepended by 's:' unless explicitly prepended with a different scope modifier. Of course, you can use the old form ('function! Name()') for defining functions if you want, as Riml aims to be as compatible as possible with VimL. There are a few exceptions where Riml and VimL aren't compatible, and these differences are explained in the section 'Incompatibilities with VimL'.

When defining a function with no parameters and no keywords (such as 'dict' or 'abort'), the parens after the function name are optional.

###Default Parameters

def fillSearchPat(pat = getDefaultSearchPat())        function! s:fillSearchPat(...)
  @/ = pat                                              let __splat_var_cpy = a:000
  return @/                                             if !empty(__splat_var_cpy)
end                                                       let pat = remove(__splat_var_cpy, 0)
                                                        else
                                                          let pat = s:getDefaultSearchPat()
                                                        endif
                                                        @/ = pat
                                                        return @/
                                                      endfunction

Default parameters must be the last parameters given to a function, but there can be more than one default parameter. Also, a splat parameter (... or *argName) can come after default parameters. Splats parameters and splat arguments will be explained in the next section.

We can now call the function 'fillSearchPat' without any arguments and it will use the default parameter.

###Splat Parameters

A splat parameter is a formal parameter to a function starting with a '*'. It must be the last parameter given to a function.

def my_echo(*words)                             function! s:my_echo(...)
  echo words                                      echo a:000
end                                             endfunction
my_echo("hello", "world")                       call my_echo("hello", "world")

=> ["hello", "world"]

###Splat Arguments

Splat arguments are splats used in a function call context. With the function my_echo defined in the previous section, here's an example at work:

words = ["hello", "world"]                      let s:words = ["hello", "world"]
echo 'without splat:'                           echo 'without splat:'
my_echo(words)                                  call my_echo(s:words)
echo 'with splat:'                              echo 'with splat:'
my_echo(*words)                                 call call('my_echo', s:words)

=> without splat:
=> [["hello", "world"]]

=> with splat:
=> ["hello", "world"]

The way to think about how splat arguments work is that the list variable that's splatted is broke into its constituent parts, just like in Ruby. So, my_echo(*words) is equivalent to my_echo("hello", "world") in this example. Notice how you can now pass the exact same arguments your function received to another function by splatting a parameter and passing it on to another function.

def some_func(*args)
  other_func(*args) " passes same arguments along to other function.
end

Classes

###Basic Class

                                                   function! s:SID()
                                                     if exists('s:SID_VALUE')
                                                       return s:SID_VALUE
                                                     endif
                                                     let s:SID_VALUE = matchstr(expand('<sfile>'), '<SNR>\zs\d\+\ze_SID$')
                                                     return s:SID_VALUE
                                                   endfunction

class MyClass                                      function! s:MyClassConstructor(data, otherData, ...)
  def initialize(data, otherData, *options)          let myClassObj = {}
    self.data = data                                 let myClassObj.data = a:data
    self.otherData = otherData                       let myClassObj.otherData = a:otherData
    self.options = options                           let myClassObj.options = a:000
  end                                                let myClassObj.getData = function('<SNR>' . s:SID() . '_s:MyClass_getData')
                                                     let myClassObj.getOtherData = function('<SNR>' . s:SID() . '_s:MyClass_getOtherData')
  defm getData                                       return myClassObj
    return self.data                               endfunction
  end
                                                   function! <SID>s:MyClass_getdata() dict
  defm getOtherData                                  return self.data
    return self.otherData                          endfunction
  end
end                                                function! <SID>s:MyClass_getOtherData() dict
                                                     return self.otherData
                                                   endfunction

In this basic example of a class, we see a *splat variable. This is just a convenient way to refer to 'a:000' in the body of a function. Splat variables are optional parameters and get compiled to '...'.

Classes can only be defined once, and cannot be reopened. Public member functions are defined with 'defm'. If you want to create a non-public function inside a class, use 'def'. To create an instance of this class, simply:

obj = new MyClass('someData', 'someOtherData')

Classes have a default scope modifier of 's:'. That is, they cannot be instantiated outside the script in which they are defined. In order to allow them to be instantiated in any script file, you must declare the class with the explicit scope modifier of 'g:'. For example:

class g:MyClass
  ...
end

In any one Riml-generated VimL file, there is at most 1 generated s:SID() function. This generated function will be omitted in the rest of this README for brevity, but every Riml file that has a class with a member function will have this code in the compiled output.

###Class Inheritance

class Translation                                  function! s:TranslationConstructor(input)
  def initialize(input)                              let translationObj = {}
    self.input = input                               let translationObj.input = a:input
  end                                                return translationObj
end                                                endfunction

class FrenchToEnglishTranslation < Translation     function! s:FrenchToEnglishTranslationConstructor(input)
  defm translate                                     let frenchToEnglishTranslationObj = {}
    if (self.input == "Bonjour!")                    let translationObj = s:TranslationConstructor(a:input)
      echo "Hello!"                                  call extend(frenchToEnglishTranslationObj, translationObj)
    else                                             let frenchToEnglishTranslationObj.translate = function('<SNR>' . s:SID() . '_s:FrenchToEnglishTranslation_translate')
      echo "Sorry, I don't know that word."          return frenchToEnglishTranslationObj
    end                                            endfunction
  end
end                                                function! <SID>s:FrenchToEnglishTranslation_translate() dict
                                                     if (self.input ==# "Bonjour!")
translation = new                                      echo "Hello!"
\ FrenchToEnglishTranslation("Bonjour!")             else
translation.translate()                                echo "Sorry, I don't know that word."
                                                     endif
                                                   endfunction

                                                   let s:translation = s:TranslationConstructor("Bonjour!")
                                                   call s:translation.translate()
=> "Hello!"

Classes that inherit must have their superclass defined before inheritance takes place. In this example, 'Translation' is defined first, which is legal. Since 'Translation' has an initialize function and 'FrenchToEnglishTranslation' doesn't, 'FrenchToEnglishTranslation' instances use the initialize function from 'Translation', and new instances must be provided with an 'input' argument on creation. Basically, if a class doesn't provide an initialize function, it uses its superclass's.

If you look at the last line of Riml in the previous example, you'll see that it doesn't use VimL's builtin 'call' function for calling the 'translate' method on the translation object. Riml can figure out when 'call' is necessary, and will add it to the compiled VimL.

A base class and inheriting class can have different scope modifiers. For example, if you had a script-local base class and wanted to extend it but have the extending class be global, this is not a problem. Simply:

class g:GlobalClass < ScriptLocalClass
  ...
end

###Using 'super'

class Car                                             function! s:CarConstructor(make, model, color)
  def initialize(make, model, color)                    let carObj = {}
    self.make = make                                    let carObj.make = a:make
    self.model = model                                  let carObj.model = a:model
    self.color = color                                  let carObj.color = a:color
  end                                                 endfunction
end

class HotRod < Car                                    function! s:HotRodConstructor(make, model, color, topSpeed)
  def initialize(make, model, color, topSpeed)          let hotRodObj = {}
    self.topSpeed = topSpeed                            let hotRodObj.topSpeed = a:topSpeed
    super(make, model, color)                           let carObj = s:CarConstructor(a:make, a:model, a:color)
  end                                                   call extend(hotRodObj, carObj)
                                                        let hotRodObj.drive = function('<SNR>' . s:SID() . '_s:HotRod_drive')
  defm drive                                            return hotRodObj
    if self.topSpeed > 140                            endfunction
      echo "Ahhhhhhh!"
    else                                              function! <SID>s:HotRod_drive() dict
      echo "Nice"                                       if self.topSpeed ># 140
    end                                                   echo "Ahhhhhhh!"
  end                                                   else
end                                                       echo "Nice"
                                                        endif
newCar = new HotRod("chevy", "mustang", "red", 160)   endfunction
newCar.drive()
                                                      let s:newCar = s:HotRodConstructor("chevy", "mustang", "red", 160)
                                                      call s:newCar.drive()
=> "Ahhhhhhh!"

Use of 'super' is legal only within subclasses. If arguments are given, these arguments are sent to the superclass's function of the same name. If no arguments are given and parentheses are omitted, ('super' as opposed to 'super()'), every single argument is passed to the superclass's function. This mirrors Ruby's approach.

Super can be called from an initialize (constructor) function, a public member function ('defm'), or a non-public function ('def'). An error is given during compilation if no superclass function with that name is defined.

Compiling Riml

To compile a riml file named 'example.riml' that resides in the current directory:

$ riml -c example.riml

This will create a new VimL file named 'example.vim' in the current directory.

###riml_source

It's useful to split a project into many files. For example, imagine we're creating a plugin called 'awesome' that does something totally awesome, and it relies on another library we wrote called 'my_framework' that's also written in Riml.

Somewhere in 'awesome.riml', we have the line:

riml_source 'my_framework.riml'

This will compile the file 'my_framework.riml' and create a VimL file named 'my_framework.vim'.

In 'awesome.riml', that line will be compiled to:

source 'my_framework.vim'

This process is recursive, meaning that if 'my_framework.riml' riml_source's other files, then those files will be compiled as well.

The previous example would only work if 'my_framework.riml' were in the current working directory where the compilation command 'riml -c' was issued. In order to tell the compiler where to look for files that are being riml_source'd, you can provide an environment variable or a command-line option of colon-separated paths. For example:

riml -c awesome.riml -S 'first_dir:second_dir'

With this command, the compiler will look for files that are riml_source'd first in ./first_dir, then in ./second_dir if not found in first_dir. The same can be achieved by:

riml -c awesome.riml RIML_SOURCE_PATH='first_dir:second_dir'

Paths can either be relative or absolute. The sourced files that are compiled will end up in the same directory in which they were found.

###riml_include

Sometimes it's useful to have many files in development, but to include a file's contents into another file during the build process. This is much like the C preprocessor's #include directive.

To include a file named 'my_lib.riml':

riml_include 'my_lib.riml'

This compiles the file and includes its content in place of the riml_include directive itself. Much like riml_sourcing, the process is recursive. If 'my_lib.riml' includes files, these files are also compiled and will be part of the inclusion. Note that riml_include does not create a new file like riml_source does.

Like riml_source, riml_include looks in a set of ordered paths to find the files to include, with the default being the working directory in which the compilation command was issued. Here are some examples of commands that set the include path:

riml -c 'main.riml' -I 'lib:helpers:debug'

riml -c 'plugin_name.riml' RIML_INCLUDE_PATH='lib:modules'

Since riml_include acts as a sort of preprocessor, it cannot be issued inside of a conditional, function, or anything dynamic. It must be at the top-level (non-nested).

Also, if you are included lots of files, you don't have to worry about multiple-inclusion, or which file should be included before which, because during the compile phase the class dependencies are resolved and the inclusions are re-ordered based on this info. It's easiest to include all the dependencies you need to include for each file without worrying about repetitions or ordering.

Take a look at https://github.com/dsawardekar/portkey/blob/develop/lib/includes/portkey_inc.riml to see how you can treat a list of inclusions as a kind of header file that other files include.

Incompatibilities with VimL

Riml aims to be as compatible with VimL as possible, therefore any legal VimL should be legal Riml as well. Unfortunately, this is not 100% possible as Vim is an old and cryptic beast, and trying to create grammar for every possible VimL construct would be a nightmare. In practice, however, when I've transformed plain old VimL plugins to be Riml-compatible, only a couple of ':' needed to be placed in strategic locations for it to be valid Riml. This is explained below.

###Ex-literals

Fortunately, there are some pretty simple rules to follow to get valid Riml.

When doing anything with autocommands, normal, commands, set, ranges, etc... simply do:

:autocmd BufEnter * blahblah...

That is, prepend ':' to the line. When a line starts with ':', it passes directly through the compiler and no transformations occur. This includes string interpolation, which is ignored as well.

In Riml, when a line starts with ':' it's called an ex-literal.

Ex-literals are necessary for the following:

  • autocommands
  • command definitions
  • set
  • ranges (:h cmdline-ranges)
  • normal (:h normal)
  • mappings
  • augroups

Basically anything that isn't a class, number, string, list, dict, function call, function definition, loop or if construct, variable definition or unlet, etc... needs to be an ex-literal in Riml.

Note that, like 'echo' which isn't a builtin function (:h functions) but is still legal Riml, 'execute' is also allowed as it takes a string. This is extremely useful, as we can now use execute with a string that allows interpolation!

Imagine having to write a grammar rule for the following:

set statusline+=[%{strlen(&fenc)?&fenc:'none'}, " File encoding

Since there's no string after the '+=', it makes it very hard. So when the compiler can't parse a file correctly, prepend those lines with ':' and all should be well.

###Abbreviations

In VimL, there are abbreviations for everything; even "keywords" like 'function' can be abbreviated. In Riml, abbreviations are not allowed. This makes Riml much easier to read and understand.

Everything Else That Works

Everything not mentioned above as illegal is legal Riml. Here's a short (non-comprehensive) list of constructs which are legal Riml but not mentioned in any of the examples:

  • try/catch/finally blocks and throw
  • curly-brace variable and function names
  • while (and until) loops
  • ternary operators
  • exponents
  • line continuations
  • autoloadable variables and functions (:h autoload)
  • let unpack (:h let-unpack)
  • Much more!

Tools

  • vim-riml - Syntax highlighting and automatic indentation for Riml files.

Projects Using Riml

  • Speckle - Test your Riml scripts BDD-style with automatic compiling and a commandline vim test runner!
  • Portkey - Library that makes it easy to write scripts to move between files in any kind of structured project.
  • Ember.vim - Ember.js plugin that is to Ember.js as vim-rails is to Rails.