From 496f8a3fbbc1e60994a83f13c2240e2fdf6bbf91 Mon Sep 17 00:00:00 2001
From: ManDude <7569514+ManDude@users.noreply.github.com>
Date: Sat, 17 Apr 2021 02:50:38 +0100
Subject: [PATCH] Add `case` macro for switch-case constructs (#362)

---
 goal_src/goal-lib.gc | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/goal_src/goal-lib.gc b/goal_src/goal-lib.gc
index 46a5ce838..a838e182f 100644
--- a/goal_src/goal-lib.gc
+++ b/goal_src/goal-lib.gc
@@ -353,6 +353,20 @@
   `(none)
   )
 
+(defmacro case (switch &rest cases)
+  "A switch-case construct. switch is saved onto a local variable and compared against each case, sequentially.
+   else can be used as the default case, but it must be the last one."
+
+  (with-gensyms (sw)
+    `(let ((sw ,switch))
+        (cond ,@(apply
+                  (lambda (x) `(,@(if (eq? (first x) 'else) `(else ,@(rest x)) `((= sw ,(first x)) ,@(rest x)))))
+                   cases)
+                   )
+        )
+    )
+  )
+
 ;;;;;;;;;;;;;;;;;;;
 ;; Math Macros
 ;;;;;;;;;;;;;;;;;;;
@@ -531,7 +545,7 @@
 ;; (Fake) MIPS Macros
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-;; these are macros for MIPS instructions which we may want to keep in the source code for 
+;; these are macros for MIPS instructions which we may want to keep in the source code for
 ;; readibility/curiosity/documentation, but will not translate into any actual instructions at all
 
 ;; A macro that generates a macro for the specified instruction