update tests and README

README.md

@@ -140,6 +140,8 @@ def is-zero [num] =
   }
 ```
 
+Will only return `true` for `is-zero $ 0`
+
 ```
 def is-single-element [list] =
   match list {
@@ -148,6 +150,8 @@ def is-single-element [list] =
   }
 ```
 
+Will only return true for lists with one item, of whatever type and value.
+
 A more advanced usage example would be
 
 Checking a static prefix:
@@ -159,7 +163,13 @@ def list-starts-with-one? [list] =
   }
 ```
 
+Will return true for lists like
+`[1], [1, 2], [1, 2, 3], [1, "a"], [1, 4], [1,-1]`, but never for lists that
+don't start with a `1`.
+
+
 Or
+
 ```
 def list-has-one-a-wildcard-and-three? [list] =
   match list {
@@ -168,21 +178,37 @@ def list-has-one-a-wildcard-and-three? [list] =
   }
 ```
 
+Will return true for a list like `[1, 3, 3]` or `[1, -1, 3, 4, 5]`.
+
 And of course some classic examples using pattern matching
 
 ```
+// Gets first element of a given list
+// Example: (list-head $ [1, 2, 3]) => 1
 def list-head [list] =
   match list {
     []        -> error $ "Empty list";
     [ x | _ ] -> x;
   }
 
+// Discards the first element of a list and returns the rest
+// Example: (list-tail $ [1, 2, 3]) => [2, 3]
+def list-tail [list] =
+  match list {
+    []         -> error $ "Empty list";
+    [ _ | xs ] -> xs;
+  }
+
+// Reverses a list
+// Example: (list-reverse $ [1, 2, 3, 4]) => [4, 3, 2, 1]
 def list-reverse [list] =
   match list {
     []         -> [];
     [ x | xs ] -> concat-lists $ (list-reverse $ xs) [x];
   }
 
+// Gets a list of successive pairs for a given list
+// Example: (list-to-pairs $ [1, 2, 3, 4]) => [[1, 2], [3, 4]]
 def list-to-pairs [list] =
   match list {
     []            -> [];

test/examples/pattern_match_advanced.bl

@@ -1,5 +1,5 @@
 ---
-output: "1\n[4,3,2,1]\n[[1,2],[3,4]]\nTrue\n"
+output: "1\n[2,3,4]\n[4,3,2,1]\n[[1,2],[3,4]]\nTrue\n"
 ---
 
 module Main where
@@ -10,6 +10,12 @@ def list-head [list] =
     [ x | _ ] -> x;
   }
 
+def list-tail [list] =
+  match list {
+    []         -> error $ "Empty list";
+    [ _ | xs ] -> xs;
+  }
+
 def list-reverse [list] =
   match list {
     []         -> [];
@@ -37,6 +43,7 @@ def main [] = {
   val my-list = [1, 2, 3, 4];
 
   puts-ln $ (to-string $ (list-head $ my-list));
+  puts-ln $ (to-string $ (list-tail $ my-list));
   puts-ln $ (to-string $ (list-reverse $ my-list));
   puts-ln $ (to-string $ (list-to-pairs $ my-list));
   puts-ln $ (to-string $ (applyTwoEqualsFour? $ (+ $ 2)));

test/parser_tests/pattern_match_advanced.bl

@@ -6,6 +6,12 @@ def list-head [list] =
     [ x | _ ] -> x;
   }
 
+def list-tail [list] =
+  match list {
+    []         -> error $ "Empty list";
+    [ _ | xs ] -> xs;
+  }
+
 def list-reverse [list] =
   match list {
     []         -> [];
@@ -33,6 +39,7 @@ def main [] = {
   val my-list = [1, 2, 3, 4];
 
   puts-ln $ (to-string $ (list-head $ my-list));
+  puts-ln $ (to-string $ (list-tail $ my-list));
   puts-ln $ (to-string $ (list-reverse $ my-list));
   puts-ln $ (to-string $ (list-to-pairs $ my-list));
   puts-ln $ (to-string $ (applyTwoEqualsFour? $ (+ $ 2)));