From 45241752e6dfc6bd4d09a3c2681043a9b0f1947f Mon Sep 17 00:00:00 2001
From: Christophe de Dinechin <christophe@dinechin.org>
Date: Fri, 16 Aug 2024 19:45:19 +0200
Subject: [PATCH] trigonometrics: Add conversion from non-standard angles

Accept `cos(1/4_turn)` without emiting an `Inconsistent Unit` error.

Fixes: #1114

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>
---
 src/algebraic.cc | 17 +++++++++++++++--
 src/tests.cc     |  9 +++++----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/algebraic.cc b/src/algebraic.cc
index 3a0e524b..2a45d617 100644
--- a/src/algebraic.cc
+++ b/src/algebraic.cc
@@ -549,6 +549,7 @@ algebraic::angle_unit algebraic::adjust_angle(algebraic_g &x)
 //   If we have an angle unit, use it for the computation
 // ----------------------------------------------------------------------------
 {
+retry:
     angle_unit amode = ID_object;
     if (unit_p uobj = x->as<unit>())
     {
@@ -563,6 +564,14 @@ algebraic::angle_unit algebraic::adjust_angle(algebraic_g &x)
                 amode = ID_PiRadians;
             else if (sym->matches("grad"))
                 amode = ID_Grad;
+
+        }
+        if (amode == ID_object)
+        {
+            algebraic_g aunit = integer::make(1);
+            if (add_angle(aunit))
+                if (unit_p(+aunit)->convert(x))
+                    goto retry;
         }
         if (amode)
             x = uobj->value();
@@ -589,8 +598,12 @@ bool algebraic::add_angle(algebraic_g &x)
     }
 
     symbol_p uexpr = symbol::make(uname);
-    x = unit::make(x, uexpr);
-    return true;
+    if (algebraic_p angle = unit::make(x, uexpr))
+    {
+        x = angle;
+        return true;
+    }
+    return false;
 }
 
 
diff --git a/src/tests.cc b/src/tests.cc
index e7588095..1e49fdd2 100644
--- a/src/tests.cc
+++ b/src/tests.cc
@@ -168,10 +168,7 @@ void tests::run(bool onlyCurrent)
     if (onlyCurrent)
     {
         here().begin("Current");
-        // eqnlib_columns_and_beams();
-        demo_ui();
-        demo_math();
-        demo_pgm();
+        exact_trig_cases();
     }
     else
     {
@@ -3761,6 +3758,10 @@ void tests::exact_trig_cases()
             .expect("-1/2");
     }
 
+    step("Conversion from non-standard units")
+        .test(CLEAR, "1/8_turn COS", ENTER)
+        .expect("0.70710 67811 87");
+
     step("Cleaning up")
         .test(CLEAR, "SmallFractions DEG", ENTER).noerror();
 }