From 610ad9a4eb9ba0376a6763d05df2342f71814680 Mon Sep 17 00:00:00 2001
From: Robbie Gleichman <rgleichman@gmail.com>
Date: Fri, 6 Jan 2017 17:29:27 -0800
Subject: [PATCH] Add advantages.hs which shows some of the advantages of a
 visual syntax over text.

---
 examples/advantages.hs | 131 +++++++++++++++++++++++++++++++++++++++++
 todo.md                |   2 +
 2 files changed, 133 insertions(+)
 create mode 100644 examples/advantages.hs

diff --git a/examples/advantages.hs b/examples/advantages.hs
new file mode 100644
index 0000000..08b09dd
--- /dev/null
+++ b/examples/advantages.hs
@@ -0,0 +1,131 @@
+{-Advantages of Glance:
+
+The following are several admittedly contrived examples demonstrating some
+of the advantages of Glance over textual code.
+
+
+1. Display out of order arguments:
+
+The function "syntaxGraphToTuple" is a simple function that converts the
+product type "SyntaxGraph" to a tuple.
+
+syntaxGraphToTuple (SyntaxGraph a b c d e) = (a, b, c, d, e)
+-}
+syntaxGraphToTuple (SyntaxGraph a b c d e) = (a, b, c, d, e)
+
+{-
+Below is a version of syntaxGraphToTuple where some of the items in the tuple have
+been swapped.
+
+badSyntaxGraphToTuple (SyntaxGraph a b c d e) = (e, b, c, d, a)
+-}
+badSyntaxGraphToTuple (SyntaxGraph a b c d e) = (e, b, c, d, a)
+{- In the Glance image of badSyntaxGraphToTuple, it is immediately apparent that
+some of the tuple arguments are out of order.
+
+
+2. Reduce obfuscation:
+
+Glance conveniently eliminates long and unnecessary binding chains. For example,
+Glance simplifies the following obfuscated function
+
+y x = g where
+ c = p
+ u = 2 * x
+ v = c
+ p = u
+ g = v
+
+to just
+y x = 2 * x
+-}
+
+y x = g where
+ c = p
+ u = 2 * x
+ v = c
+ p = u
+ g = v
+
+{-
+3. Make recursion visible:
+
+Consider the recursive definition of the Fibonacci sequence
+
+fibs = cons 0 (cons 1 (zipWith (+) fibs (tail fibs)))
+
+In Glance, the recursive usages of fibs are explicitly shown with lines
+looping from the result back into the nested icon.
+-}
+
+fibs = cons 0 (cons 1 (zipWith (+) fibs (tail fibs)))
+
+{-
+4. Simplified syntax:
+
+In Haskell, there are many ways to write code that means the same thing.
+
+For example, all of these lines of code mean exactly the same thing:
+y = f (g x)
+y = f $ g x
+y = f $ g $ x
+y = (f . g) x
+y = f . g $ x
+
+In Glance, these are all rendered the same.
+-}
+y = (f . g) x
+
+{-
+A few more examples:
+
+notZero 0 = False
+notZero _ = True
+
+and
+
+notZero x = case x of
+  0 -> False
+  _ -> True
+
+are both rendered as
+-}
+notZero x = case x of
+  0 -> False
+  _ -> True
+{-
+
+In Haskell, guards are not expressions, so having multiple levels of guards
+is quite awkward. The textual function below, for example,
+requires two superfluous variables, temp1 and temp2.
+
+In Glance, this sort of code is no problem.
+
+foo x y
+  | x > 0 = let
+      temp1
+        | y > 0 = 'a'
+        | otherwise = 'b'
+      in temp1
+  | otherwise = let
+      temp2
+        | y > 0 = 'c'
+        | otherwise = 'd'
+      in temp2
+
+-}
+
+foo x y
+  | x > 0 = let
+      temp1
+        | y > 0 = 'a'
+        | otherwise = 'b'
+      in temp1
+  | otherwise = let
+      temp2
+        | y > 0 = 'c'
+        | otherwise = 'd'
+      in temp2
+
+{-In future version of Glance, nested guards/cases could be rendered using a 2D grid.
+-}
diff --git a/todo.md b/todo.md
index feb6a97..ac5f8b2 100644
--- a/todo.md
+++ b/todo.md
@@ -11,6 +11,8 @@
 * Fix the arrowheads being too big for SyntaxGraph drawings.
 
 ### Visual todos
+* Use pattern colors for pattern literal text boxes.
+
 * Draw bounding boxes for lambdas (use dashed lines)
 
 * Use different line styles (e.g. dashed, solid, wavy) in addition to colors