mers/docs/syntax_cheat_sheet.md

mers syntax cheat sheet

Types

• bool
• int
• float
• string
• tuple: [<type1> <type2> <type3> <...>]
• list: [<type> ...]
• function: fn(<input-output-map>) (might change? depends on implementation of generics)
• thread: thread(<return_type>)
• reference: &<type>
• enum: EnumName(<type>)
• one of multiple types: <type1>/<type2>/<type3>

Values

• bool
  • true or false
• int
  • decimal: 2, +2, -5, 0, ...
• float
  • decimal: 1.5, 0.5, -5.2, 2.0, ... (this is recommended for compatability and clarity)
  • whole numbers: 1.0, 1., ... (may break with future updates)
  • numbers from 0 to 1: .5 would be ambiguous following tuples, so is not supported.
• string
  • "my string" (double quotes)
  • "it's called \"<insert name>\"" (escape inner double quotes with backslash)
  • all escape sequences
    • \" double quote character
    • \\ backslash character
    • \n newline
    • \r carriage return
    • \t tab
    • \0 null
• tuple
  • [<val1> <val2> <val3> <...>]
• list
  • [<val1> <val2> <val3> <...> ...] (like tuple, but ...] instead of ])
• function
  • (<arg1> <arg2> <arg3> <...>) <statement> where <argn> is <namen> <typen>.
• thread
  • returned by the builtin function thread()
• reference
  • to a variable: &<varname>
  • to something else: usually using get() or its equivalent on a reference to a container instead of the container itself: &list.get() instead of list.get()
• enum
  • <EnumName>: <statement>

Variables

• declaration and initialization
  • <var_name> := <statement>
  • can shadow previous variables with the same name: x := 5 { x := 10 debug(x) } debug(x) prints 10 and then 5.
• assignment
  • &<var_name> = <statement>
    • modifies the value: x := 5 { &x = 10 debug(x) } debug(x) prints 10 and then 10.
  • <statement_left> = <statement_right>
    • assigns the value returned by <statement_right> to the value behind the reference returned by <statement_left>.
    • if <statement_right> returns <type>, <statement_left> has to return &<type>.
    • this is why &<var_name> = <statement> is the way it is.
  • ***<statement_left> = <statement_right>
    • same as before, but performs dereferences: &&&&int becomes &int (minus 3 references because 3 *s), so a value of type int can be assigned to it.

Statements

• value
  • 10, true, "text", "[]", etc
• tuple
  • [<statement1> <statement2> <...>]
• list
  • [<statement1> <statement2> <...> ...]
• variable
  • <var_name> (if the name of the variable isn't a value or some other kind of statement)
• function call
  • <fn_name>(<arg1> <arg2> <...>)
• function definition
  • fn <fn_name>(<arg1> <arg2> <...>) <statement> where <argn> is <namen> <typen>
• block
  • { <statement1> <statement2> <...> }
• if
  • if <condition> <statement> (if true println("test"))
  • if <condition> <statement> else <statement> (if false println("test") else println("value was false"))
• loop
  • loop <statement>
  • if the statement returns a value that matches, the loop will end and return the matched value
  • the loop's return type is the match of the return type of the statement
• for loop
  • for <var_name> <iterator> <statement>
  • in each iteration, the variable will be initialized with a value from the iterator.
  • iterators can be lists, tuples, or functions.
  • for function iterators, as long as the returned value matches, the matched value will be used. if the value doesn't match, the loop ends.
  • if the statement returns a value that matches, the loop will end and return the matched value
  • the loop's return type is the match of the return type of the statement or [] (if the loop ends because the iterator ended)
• switch
  • switch <var_name> { <arm1> <arm2> <...> }
    • where <armn> is <typen> <statementn>
    • if the variable's value is of type <typen>, <statementn> will be executed.
    • if the variables type is included multiple times, only the first match will be executed.
    • within the statement of an arm, the variables type is that specified in <typen>, and not its original type (which may be too broad to work with)
  • switch! <var_name> { <arm1> <arm2> <...> }
    • same as above, but all types the variable could have must be covered
    • the additional [] in the return type isn't added here since it is impossible not to run the statement of one of the arms.
• match
  • match <var_name> { <arm1> <arm2> <...> }
    • where <armn> is <statement> <statement>
    • each arm has a condition statement an an action statement.
    • if the value returned by the condition statement matches, the matched value is assigned to the variable and the action statement is executed.
    • only the first matching arm will be executed. if no arm was executed, [] is returned.
• fixed-indexing
  • <statement>.n where n is a fixed number (not a variable, just 0, 1, 2, ...)
  • <statement> must return a tuple or a reference to one. <statement>.n then refers to the nth value in that tuple.
  • for references to a tuple, references to the inner values are returned.
• enum
  • <EnumName>: <statement>
• type definition
  • type <name> <type> (type Message [string string])
• macros
  • !(<macro_type> <...>)
  • !(mers { <code> })
    • compiles and runs the code at compile-time, then returns the computed value at runtime.
  • !(mers <file_path>) or !(mers "<file path with spaces and \" double quotes>")
    • same as above, but reads code from a file instead
    • path can be relative

Matching

• values that don't match
  • []
  • false
• values that match
  • [v] -> v
  • v -> v unless otherwise specified
• invalid
  • [v1 v2] or any tuple whose length isn't 0 or 1