Trac 18153: sage to gap conversion for infinity

sagemath · Apr 10, 2015 · cc3297d · cc3297d
1 parent 4ec9f5f
commit cc3297d
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Showing 2 changed files with 29 additions and 3 deletions.
diff --git a/src/sage/libs/gap/element.pyx b/src/sage/libs/gap/element.pyx
@@ -880,7 +880,8 @@ cdef class GapElement(RingElement):
             sage: libgap(3) ^ Infinity
             Traceback (most recent call last):
             ...
-            ValueError: libGAP: Error, Variable: 'Infinity' must have a value
+            ValueError: libGAP: Error, no method found! Error, no 1st choice
+            method found for `InverseMutable' on 1 arguments
         """
         if not isinstance(right, GapElement):
             libgap = self.parent()
@@ -1030,9 +1031,9 @@ cdef class GapElement(RingElement):
             sage: libgap.eval('5 + 7*E(3)').sage()
             7*zeta3 + 5
 
-            sage: libgap.eval('infinity').sage()
+            sage: libgap(Infinity).sage()
             +Infinity
-            sage: libgap.eval('-infinity').sage()
+            sage: libgap(-Infinity).sage()
             -Infinity
 
             sage: libgap(True).sage()

diff --git a/src/sage/rings/infinity.py b/src/sage/rings/infinity.py
@@ -1466,6 +1466,18 @@ def _sympy_(self):
         import sympy
         return -sympy.oo
 
+    def _gap_init_(self):
+        r"""
+        Conversion to gap and libgap.
+
+        EXAMPLES::
+
+            sage: gap(-Infinity)
+            -infinity
+            sage: libgap(-Infinity)
+            -infinity
+        """
+        return '-infinity'
 
 class PlusInfinity(_uniq, AnInfinity, PlusInfinityElement):
 
@@ -1523,6 +1535,19 @@ def _sympy_(self):
         import sympy
         return sympy.oo
 
+    def _gap_init_(self):
+        r"""
+        Conversion to gap and libgap.
+
+        EXAMPLES::
+
+            sage: gap(+Infinity)
+            infinity
+            sage: libgap(+Infinity)
+            infinity
+        """
+        return 'infinity'
+
 InfinityRing = InfinityRing_class()
 infinity = InfinityRing.gen(0)
 Infinity = infinity