From bbce87e26a262a2f442b86608bae06bfd42f3b0e Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Fri, 16 Oct 2020 13:01:19 -0400
Subject: First expression diagram

---
 tutorial/evalexp.bqn   | 19 ++++++++++++++-----
 tutorial/expression.md |  7 +++----
 2 files changed, 17 insertions(+), 9 deletions(-)

(limited to 'tutorial')

diff --git a/tutorial/evalexp.bqn b/tutorial/evalexp.bqn
index 304301e5..5d922af1 100644
--- a/tutorial/evalexp.bqn
+++ b/tutorial/evalexp.bqn
@@ -1,10 +1,17 @@
 wh ← 10.75‿24
-pad← wh×1.5‿1
+pad← wh×2‿1
 t ← 10
 
-ps ← >⟨"stroke"‿"#585552","style"‿"fill:none","stroke-width"‿"2"⟩
-rc ← >⟨"class"‿"code","stroke-width"‿"1","rx"‿"12"⟩
-gr ← "g" Attr >⟨"font-family"‿"BQN,monospace", "font-size"‿"18px"⟩
+ps ← At "class=Paren|stroke=currentColor|fill=none|stroke-width=1"
+rc ← At "class=code|stroke-width=1|rx=10"
+gr ← "g" At "font-family=BQN,monospace|font-size=18px"
+gt ← "g" At "text-anchor=middle"
+gb ← "g" At "class=codeCover|stroke-width=6|stroke-linejoin=round"
+gf ← "g" At "font-size=15px|opacity=0.9"
+Shadow ← {
+  t ← (⟨0,0‿¯2⟩+⌜𝕨) ("text" Attr Pos)⊸Enc¨ (⊢≍Highlight¨) ⥊¨𝕩
+  gt Enc ⟨gb,gf⟩ Enc¨<˘ t
+}
 
 DrawEval←{
   ix←𝕩⊏˜i←/𝕩≠' '
@@ -18,12 +25,14 @@ DrawEval←{
   m←1+⌈´d←+`⊸×⌾(rev⊸⊏)fn
 
   pt ← f/⍉> wh×⟨i,d⟩
-  off← (o ⊏ ∾⟜(whׯ1‿m))⊸- pt
+  off← (o ⊏ ∾⟜(whׯ1.25‿m))⊸- pt
   pd ← pt (<(wh×0.6‿0.1)⊸+)⊸∾⟜⌽˘ off
   dim← (wh×⟨≠𝕩,2+m⟩)+2‿0×pad
+  tp ← <˘pt+(1+wh÷2‿3)+⎉1(0‿1×⌜˜f/¬fn)×off
   (512‿0⊸⌈⊸(⊣∾˜(t+pad)-˜-˜÷2˙)dim+2×t) SVG gr Enc ∾⥊¨⟨
     <"rect" Elt rc∾(Pos-pad)∾"width"‿"height"≍˘FmtNum¨dim
     <"text" Enc Highlight 𝕩
     (<"path" Elt ps∾"d"≍○<·∾"Mvh"∾⟜Fmt¨⊢)˘ pd
+    <tp Shadow f/ix
   ⟩
 }
diff --git a/tutorial/expression.md b/tutorial/expression.md
index 59fe827c..39738d51 100644
--- a/tutorial/expression.md
+++ b/tutorial/expression.md
@@ -57,10 +57,9 @@ For a longer example, here's an expression for the [volume of a sphere](https://
 
 The evaluation order is shown below, with the function `⋆` on the first line evaluated first, then `×` on the next, and so on. The effect of the parentheses is that `÷` is evaluated before the leftmost `×`.
 
-     =              2⋆3
-                π ×
-         4÷3
-        (   ) ×
+<!--SVG evalexp.bqn
+DrawEval "(4÷3) × π × 2⋆3"
+-->
 
 The following rule might help you to internalize this system in addition to identifying when parentheses are needed: an expression never needs to end with a parenthesis, or contain two closing parentheses in a row. If it does, at least one set of parentheses can be removed.
 
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