ginger/docs/syntax.md
2014-10-06 17:44:07 -04:00

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# Syntax
This document describes the ginger syntax and data-structures, and how they are
evaluated.
# Goals
I have some immediate goals I'm trying to achieve with this syntax:
* Everything is strings (except numbers, functions, and data structures). There
is no symbol type, atom type, keyword type, etc... they're all just strings.
* There is no `defmacro`. Macro creation and usage is simply an inherent feature
of the language syntax.
# Walkthrough
This is a number which evalutates to 5:
```
5
```
This is a string, it can contain anything:
```
"! I'm the king of the world !"
```
This is a list. It evaluates to a linked-list of four strings:
```
("a" "b" "c" "d")
```
This is a vector of those same elements. It's like a list, but has some slightly
different properties. We'll mostly be using lists:
```
["a" "b" "c" "d"]
```
This is a string
```
"+"
```
`:` is the evaluator. A string beginning with `:` is evaluated to whatever it
references. This evaluates to a function which adds its arguments:
```
":+"
```
This evaluates to list whose elements are a function and two numbers:
```
(":+" 1 2)
```
A list whose first element is a `:` calls the second element as a function with
the rest of the elements as arguments. This evaluates to the number 5:
```
(":" ":+" 1 2)
```
A bare string (lacking in `"`) is automatically prefixed with a `:`, if it
doesn't already have one. So `":+"`, `:+`, and `+`, are equivalent. `":"` and
`:` are also equivalent. This is equivalent to the previous example:
```
(: + 1 2)
```
The `fn` function can be used to define a new function. Note the `.` instead of
`:`. We'll cover that in a bit. This evaluates to an anonymous function which
adds one to its argument and returns it:
```
(. fn [x]
(: + x 1))
```
The `def` function can be used to bind some value to a new variable. This
defines a variable `foo` which evaluates to the string `"bar"`:
```
(. def foo "bar")
```
This defines a variable `incr` which evaluates to a function which adds one to
its argument:
```
(. def incr
(. fn [x]
(: + x 1)))
```
This uses `defn` as a shortcut for the above:
```
(. defn incr [x]
(: + x 1))
```
There are also maps. A map's keys can be any value(?). A map's values can be any
value. This evaluates to a map with 2 key/val pairs:
```
{ "foo" foo
"bar" (: incr 4) }
```
`.` is the half-evaluator. It only works on lists, and runs the function given
in the first argument with the unevaluated arguments (even if they have `:`).
You can generate new code to run on the fly (macros) using the normal `fn`. This
evaluates to a `let`-like function, except it forces you to use the capitalized
variable names in the body (utterly useless):
```
#
# eval evaluates a given value (either a string or list). It has been
# implicitely called on all examples so far.
#
# elem-map maps over every element in a list, embedded or otherwise
#
# capitalize looks for the first letter in a string and capitalizes it
#
(. defn caplet [mapping body...]
(. eval
(. let
(: elem-map
(. fn [x]
(. if (: mapping (: slice x 1))
(: capitalize x)
x))
mapping)
body...)))
#Usage
(. caplet [foo "this is foo"
dog "this is dog"]
(: println Foo)
(: println Dog))
```