From 429d0d98fe5197eabdc04bcd130ed8b98866f601 Mon Sep 17 00:00:00 2001
From: LordBaryhobal <lordbaryhobal@gmail.com>
Date: Thu, 21 May 2026 07:53:56 +0200
Subject: [PATCH] feat: update railroad diagrams with revised syntax

---
 syntax/midas.typ | 175 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 126 insertions(+), 49 deletions(-)

diff --git a/syntax/midas.typ b/syntax/midas.typ
index 17db6d6..56d2884 100644
--- a/syntax/midas.typ
+++ b/syntax/midas.typ
@@ -1,4 +1,15 @@
-#import "@preview/fervojo:0.1.1": render
+#import "@preview/fervojo:0.1.1": default-css, render
+
+#let extra-css = ```css
+svg.railroad .terminal rect {
+  fill: #F7DCD4;
+}
+```
+#let css = default-css() + bytes(extra-css.text)
+
+#let variable = ```
+{[`variable` 'identifier'*"."]}
+```
 
 #let value = ```
 {[`value` <
@@ -8,90 +19,156 @@
 >]}
 ```
 
-#let constraint = ```
-{[`constraint` <"_", 'value'> <">", "<", ">=", "<=", "==", "!="> <"_", 'value'>]}
+#let lambda-value = ```
+{[`lambda-value` <"_", 'value', 'variable'>]}
 ```
 
-#let type-with-constraints = ```
-{[`type-with-constraints` 'identifier' <!, ["+" "(" 'constraint' ")"] * !>]}
+#let lambda-operator = ```
+{[`lambda-operator` <">", "<", ">=", "<=", "==", "!=">]}
+```
+
+#let lambda = ```
+{[`lambda` 'lambda-value' ['lambda-operator' 'lambda-value']*!]}
+```
+
+#let simple-type = ```
+{[`simple-type` 'identifier' <!, "?">]}
+```
+
+#let template = ```
+{[`template` "[" 'simple-type' "]"]}
+```
+
+#let type = ```
+{[`type` 'identifier' <!, 'template'> <!, "?">]}
+```
+
+#let constraint = ```
+{[`constraint` <'identifier', 'lambda'>]}
+```
+
+#let wrapped-constraint = ```
+{[`wrapped-constraint` <'constraint', ["(" 'constraint' ")"]>]}
+```
+
+#let constraints = ```
+{[`constraints` 'wrapped-constraint'*"&"]}
 ```
 
 #let type-property = ```
-{[`type-property` 'identifier' ":" 'type-with-constraints']}
+{[`type-property` 'identifier' ":" 'type' <!, ["where" 'constraints']>]}
 ```
 
 #let type-body = ```
 {[`type-body` "{" <!, 'type-property'*!> "}"]}
 ```
 
-#let operation-type = ```
-{[`operation-type` "<" 'type-with-constraints' ">"]}
-```
-
 #let type-statement = ```
-{[`type-statement` "type" 'identifier' "<" 'type-with-constraints'*"," ">" <!, 'type-body'>]}
+{[`type-statement` "type" 'identifier' <!, 'template'> <[["(" 'type' ")"] <!, ["where" 'constraints']>], 'type-body'>]}
 ```
 
-#let operation-statement = ```
-{[`operation-statement` "op" 'operation-type' "operator" 'operation-type' "=" 'operation-type']}
+#let op-definition = ```
+{[`op-definition` "op" <'identifier', ["__" 'identifier' "__"]> "(" 'type' ")" "->" 'type']}
 ```
 
-#let constraint-statement = ```
-{[`constraint-statement` "constraint" 'identifier' "=" 'constraint']}
+#let extend-statement = ```
+{[`extend-statement` "extend" 'type' "{" <!, 'op-definition'*!> "}"]}
+```
+
+#let predicate-statement = ```
+{[`predicate-statement` "predicate" 'identifier' "(" 'identifier' ":" 'type' ")" "=" 'constraints']}
 ```
 
 #let statement = ```
-{[`statement` <'type-statement', 'operation-statement', 'constraint-statement'>]}
+{[`statement` <'type-statement', 'extend-statement', 'predicate-statement'>]}
 ```
 
 #let rules = (
-  value,
-  constraint,
-  type-with-constraints,
-  type-property,
-  type-body,
-  operation-type,
-  type-statement,
-  operation-statement,
-  constraint-statement,
-  statement,
+  variable: variable,
+  value: value,
+  lambda-value: lambda-value,
+  lambda-operator: lambda-operator,
+  lambda: lambda,
+  simple-type: simple-type,
+  template: template,
+  type: type,
+  constraint: constraint,
+  wrapped-constraint: wrapped-constraint,
+  constraints: constraints,
+  type-property: type-property,
+  type-body: type-body,
+  type-statement: type-statement,
+  op-definition: op-definition,
+  extend-statement: extend-statement,
+  predicate-statement: predicate-statement,
+  statement: statement,
+)
+
+#let inline = (
+  "value",
+  "variable",
+  "lambda-operator",
+  "template",
+  "lambda",
+  "simple-type",
+  "wrapped-constraint",
+  "type-property",
+  "type-body",
+  "op-definition",
+  "type-statement",
+  "extend-statement",
+  "predicate-statement",
 )
 
 #set text(font: "Source Sans 3")
 
-= Midas type definition syntax
+#title[Midas type definition syntax]
 
-#for rule in rules {
-  render(rule)
-}
+= Outline
 
-/*
-#let by-name = (
-  value: value,
-  constraint: constraint,
-  type-with-constraints: type-with-constraints,
-  type-property: type-property,
-  type-body: type-body,
-  operation-type: operation-type,
-  type-statement: type-statement,
-  operation-statement: operation-statement,
-  constraint-statement: constraint-statement,
+#box(
+  columns(
+    2,
+    outline(title: none),
+  ),
+  height: 8cm,
+  stroke: 1pt,
+  inset: 1em,
 )
 
+= Statements and expressions
+
+#for (name, rule) in rules.pairs().rev() {
+  [== #name]
+  render(rule, css: css)
+}
+
 #let substitute(base-rule) = {
   let new-rule = base-rule
-  for (key, rule) in by-name.pairs() {
-    new-rule = new-rule.replace("'" + key + "'", rule.text.slice(1, -1))
+  for name in inline {
+    let rule = rules.at(name)
+    let replacement = rule.text.slice(1, -1).replace(regex("\[`.*?`"), "[")
+    replacement = "[" + replacement + "#`" + name + "`]"
+    new-rule = new-rule.replace(
+      "'" + name + "'",
+      replacement,
+    )
   }
   if new-rule != base-rule {
     new-rule = substitute(new-rule)
   }
-  return new-rule.replace(regex("`.*?`"), "")
+  return new-rule
 }
 
-#let combined = raw(substitute(statement.text))
-
-
 #set page(flipped: true)
-#render(combined)
-*/
\ No newline at end of file
+
+= Combined rules
+
+#for (name, rule) in rules.pairs() {
+  if not name in inline {
+    [== #name]
+    let combined = substitute(rule.text)
+    render(raw(combined), css: css)
+    //raw(block: true, combined)
+  }
+}