From 642f073b446cbcee3eb74bad72129fa37e4c6f46 Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jans.tuomi@gmail.com>
Date: Thu, 8 Dec 2022 14:28:00 +0200
Subject: Fix fn call with zero arguments

---
 spec.md | 36 ++++++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 14 deletions(-)

(limited to 'spec.md')

diff --git a/spec.md b/spec.md
index 953b672..934e119 100644
--- a/spec.md
+++ b/spec.md
@@ -1,28 +1,36 @@
 # Language spec
 
 - Dynamically and weakly typed, interpreted
-- Impure functions marked with ! (convention)
+- Impure functions marked with ! (convention), purity is tracked by the interpreter
 - Boolean functions marked with ? (convention)
 - Loops implemented with recursion
 
 ## Value types
 
-  Number      -3.14
-  Symbol      PI
-  Boolean     true
-  String      "foobar"
-  Vector      [1 2 3]
-  Hash map    { a 1 b 2 }
-  Function    (\[x y] (+ x y))
+    Number      -3.14
+    Symbol      PI
+    Tag         :tag
+    Boolean     true
+    String      "foobar"
+    Vector      [1 2 3]
+    Hash map    { a 1 b 2 }
+    Function    (\[x y] (+ x y))
 
 ## Syntax
 
 ### Function calls
 
-A sequence of values surrounded by parens is considered a function call In a function call, the first element must evaluate to a function value. The function will be invoked with the rest of the elements as arguments to the function.
+A sequence of values surrounded by parens is considered a function call In a function call, the first element must evaluate to a function value. The function will be invoked with the rest of the elements as arguments to the function. A function call with no arguments evaluates to the function itself.
 
 ### Function definition
-Calling the builtin variadic function '\' constructs a new function. The first argument must be a vector of symbols (parameter list). The rest of the arguments form the function body. The evaluated value of the last argument is returned as the return value of the function.
+
+Calling the builtin variadic function `\` constructs a new function. The first argument must be a vector of symbols (parameter list). The rest of the arguments form the function body. The evaluated value of the last argument is returned as the return value of the function.
+
+Memoized pure functions can be created with a special `let memo`-binding:
+
+    (let memo f (\[x] x))
+
+Impure functions can be created with the builtin `\!`.
 
 ### Currying
 
@@ -43,20 +51,20 @@ Evaluates second argument and stores the resulting value in the environment.
 `\`  
 Defines a function.
 
-    (\[x y] + x y)
+    (\[x y] (+ x y))
 
 `print!`  
-Prints a value and a newline.
+Prints a value without a newline.
 
     (print! PI)
 
 `match`  
-Matches first argument (value) to even positioned arguments (matchers). On match (at position i), evaluates the odd positioned argument (branch) right after it (at position i + 1). If given an even number of arguments, the last argument will act as the default branch.
+Matches first argument (value) to even positioned arguments (matchers). On match (at position i), evaluates the odd positioned argument (branch) right after it (at position i + 1).
 
     (match (sum2 1 1)
         2 (do-thing)
         3 (do-other-thing)
-        (do-else))
+        otherwise (do-else))
 
 `head`  
 Gets the first element of a vector.
-- 
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