Add "needs" tags for giac and libgiac

src/doc/en/prep/Calculus.rst

@@ -316,8 +316,9 @@ help it look nicer in the browser?
     - 1/10*(sqrt(5) - 3)*log(2*x^2 + x*(sqrt(5) - 1) + 2)/(sqrt(5) - 1)
     + 1/5*log(x + 1)
 
-Some integrals are a little tricky, of course. Sage tries hard to integrate using Maxima, Giac and Sympy::
+Some integrals are a little tricky, of course. Sage tries hard to integrate using Maxima, Sympy, and (optionally, if installed) Giac. The following can only be integrated by Giac::
 
+    sage: # needs sage.libs.giac
     sage: integral(1/(1+x^10),x)
     ...1/20*(sqrt(5) + 1)*arctan((4*x + sqrt(-2*sqrt(5) + 10))/(sqrt(5) + 1))
     + 1/20*(sqrt(5) + 1)*arctan((4*x - sqrt(-2*sqrt(5) + 10))/(sqrt(5) + 1))

src/sage/calculus/calculus.py

@@ -385,7 +385,7 @@
     2*pi
 
 Ensure that :issue:`25626` is fixed. As the form of the answer is dependent of
-the giac version, we simplify it (see :issue:`34037`). ::
+the giac version, we simplify it (see :issue:`34037`)::
 
     sage: t = SR.var('t')
     sage: integrate(exp(t)/(t + 1)^2, t, algorithm='giac').full_simplify()
@@ -568,6 +568,7 @@ def symbolic_sum(expression, v, a, b, algorithm='maxima', hold=False):
 
     An example of this summation with Giac::
 
+        sage: # needs giac
         sage: symbolic_sum(1/(1+k^2), k, -oo, oo, algorithm='giac').factor()
         pi*(e^(2*pi) + 1)/((e^pi + 1)*(e^pi - 1))
 
@@ -843,7 +844,7 @@ def symbolic_product(expression, v, a, b, algorithm='maxima', hold=False):
 
       - ``'maxima'`` -- use Maxima (the default)
 
-      - ``'giac'`` -- use Giac
+      - ``'giac'`` -- use Giac (optional)
 
       - ``'sympy'`` -- use SymPy
 
@@ -1296,7 +1297,7 @@ def limit(ex, dir=None, taylor=False, algorithm='maxima', **argv):
 
     With the standard package Giac::
 
-        sage: from sage.libs.giac.giac import libgiac     # random
+        sage: # needs sage.libs.giac
         sage: (exp(-x)/(2+sin(x))).limit(x=oo, algorithm='giac')
         0
         sage: limit(e^(-1/x), x=0, dir='right', algorithm='giac')
@@ -1564,7 +1565,7 @@ def laplace(ex, t, s, algorithm='maxima'):
 
       - ``'sympy'`` -- use SymPy
 
-      - ``'giac'`` -- use Giac
+      - ``'giac'`` -- use Giac (optional)
 
     .. NOTE::
 
@@ -1668,7 +1669,7 @@ def laplace(ex, t, s, algorithm='maxima'):
         (0, True)
         sage: F        # random - sympy <1.9 includes undefined heaviside(0) in answer
         1
-        sage: laplace(dirac_delta(t), t, s, algorithm='giac')
+        sage: laplace(dirac_delta(t), t, s, algorithm='giac')  # needs giac
         1
 
     Heaviside step function can be handled with different interfaces.
@@ -1677,8 +1678,9 @@ def laplace(ex, t, s, algorithm='maxima'):
         sage: laplace(heaviside(t-1), t, s)
         e^(-s)/s
 
-    Try with giac::
+    Try with giac, if it is installed::
 
+        sage: # needs giac
         sage: laplace(heaviside(t-1), t, s, algorithm='giac')
         e^(-s)/s
 
@@ -1691,6 +1693,7 @@ def laplace(ex, t, s, algorithm='maxima'):
 
     Testing Giac::
 
+        sage: # needs giac
         sage: var('t, s')
         (t, s)
         sage: laplace(5*cos(3*t-2)*heaviside(t-2), t, s, algorithm='giac')
@@ -1699,13 +1702,14 @@ def laplace(ex, t, s, algorithm='maxima'):
     Check unevaluated expression from Giac (it is locale-dependent, see
     :issue:`22833`)::
 
-        sage: var('n')
-        n
+        sage: # needs giac
+        sage: n = SR.var('n')
         sage: laplace(t^n, t, s, algorithm='giac')
         laplace(t^n, t, s)
 
     Testing SymPy::
 
+        sage: n = SR.var('n')
         sage: F, a, cond = laplace(t^n, t, s, algorithm='sympy')
         sage: a, cond
         (0, re(n) > -1)
@@ -1806,7 +1810,7 @@ def inverse_laplace(ex, s, t, algorithm='maxima'):
 
       - ``'sympy'`` -- use SymPy
 
-      - ``'giac'`` -- use Giac
+      - ``'giac'`` -- use Giac (optional)
 
     .. SEEALSO::
 
@@ -1843,11 +1847,13 @@ def inverse_laplace(ex, s, t, algorithm='maxima'):
 
     The same instance with Giac::
 
+        sage: # needs giac
         sage: inverse_laplace(1/s^2*exp(-s), s, t, algorithm='giac')
         (t - 1)*heaviside(t - 1)
 
     Transform a rational expression::
 
+        sage: # needs giac
         sage: inverse_laplace((2*s^2*exp(-2*s) - exp(-s))/(s^3+1), s, t,
         ....:                 algorithm='giac')
         -1/3*(sqrt(3)*e^(1/2*t - 1/2)*sin(1/2*sqrt(3)*(t - 1))
@@ -1864,7 +1870,7 @@ def inverse_laplace(ex, s, t, algorithm='maxima'):
         dirac_delta(t)
         sage: inverse_laplace(1, s, t, algorithm='sympy')
         dirac_delta(t)
-        sage: inverse_laplace(1, s, t, algorithm='giac')
+        sage: inverse_laplace(1, s, t, algorithm='giac')  # needs giac
         dirac_delta(t)
 
     TESTS:
@@ -1878,6 +1884,7 @@ def inverse_laplace(ex, s, t, algorithm='maxima'):
 
     Testing Giac::
 
+        sage: # needs giac
         sage: inverse_laplace(exp(-s)/s, s, t, algorithm='giac')
         heaviside(t - 1)
 
@@ -1888,12 +1895,14 @@ def inverse_laplace(ex, s, t, algorithm='maxima'):
 
     Testing unevaluated expression from Giac::
 
-        sage: n = var('n')
+        sage: # needs giac
+        sage: n = SR.var('n')
         sage: inverse_laplace(1/s^n, s, t, algorithm='giac')
         ilt(1/(s^n), t, s)
 
     Try with Maxima::
 
+        sage: n = SR.var('n')
         sage: inverse_laplace(1/s^n, s, t, algorithm='maxima')
         ilt(1/(s^n), s, t)
 
@@ -1909,6 +1918,7 @@ def inverse_laplace(ex, s, t, algorithm='maxima'):
 
     Testing the same with Giac::
 
+        sage: # needs giac
         sage: inverse_laplace(cos(s), s, t, algorithm='giac')
         ilt(cos(s), t, s)
     """
@@ -2472,13 +2482,18 @@ def _find_var(name, interface=None):
 
     EXAMPLES::
 
-        sage: y = var('y')
+        sage: y = SR.var('y')
         sage: sage.calculus.calculus._find_var('y')
         y
         sage: sage.calculus.calculus._find_var('I')
         I
         sage: sage.calculus.calculus._find_var(repr(maxima(y)), interface='maxima')
         y
+
+    ::
+
+        sage: # needs giac
+        sage: y = SR.var('y')
         sage: sage.calculus.calculus._find_var(repr(giac(y)), interface='giac')
         y
     """
@@ -2585,6 +2600,7 @@ def symbolic_expression_from_string(s, syms=None, accept_sequence=False, *, pars
 
     The Giac interface uses a different parser (:issue:`30133`)::
 
+        sage: # needs giac
         sage: from sage.calculus.calculus import SR_parser_giac
         sage: symbolic_expression_from_string(repr(giac(SR.var('e'))), parser=SR_parser_giac)
         e

src/sage/calculus/functional.py

@@ -53,7 +53,7 @@ def simplify(f, algorithm='maxima', **kwds):
         sage: ex = 1/2*I*x + 1/2*I*sqrt(x^2 - 1) + 1/2/(I*x + I*sqrt(x^2 - 1))
         sage: simplify(ex)
         1/2*I*x + 1/2*I*sqrt(x^2 - 1) + 1/(2*I*x + 2*I*sqrt(x^2 - 1))
-        sage: simplify(ex, algorithm='giac')
+        sage: simplify(ex, algorithm='giac')  # needs giac
         I*sqrt(x^2 - 1)
     """
     try:

src/sage/functions/exp_integral.py

@@ -800,7 +800,7 @@ def __init__(self):
             Si(x)
             sage: sin_integral(x)._fricas_init_()
             'Si(x)'
-            sage: sin_integral(x)._giac_()                                              # needs sage.libs.giac
+            sage: sin_integral(x)._giac_()                                              # needs giac
             Si(sageVARx)
         """
         BuiltinFunction.__init__(self, "sin_integral", nargs=1,
@@ -975,7 +975,7 @@ def __init__(self):
             Ci(x)
             sage: cos_integral(x)._fricas_init_()
             'Ci(x)'
-            sage: cos_integral(x)._giac_()                                              # needs sage.libs.giac
+            sage: cos_integral(x)._giac_()                                              # needs giac
             Ci(sageVARx)
         """
         BuiltinFunction.__init__(self, "cos_integral", nargs=1,

src/sage/functions/generalized.py

@@ -253,7 +253,7 @@ def __init__(self):
             H\left(x\right)
             sage: heaviside(x)._sympy_()                                                # needs sympy
             Heaviside(x)
-            sage: heaviside(x)._giac_()                                                 # needs sage.libs.giac
+            sage: heaviside(x)._giac_()                                                 # needs giac
             Heaviside(sageVARx)
             sage: h(x) = heaviside(x)
             sage: h(pi).numerical_approx()
@@ -413,7 +413,7 @@ class FunctionSignum(BuiltinFunction):
         sign(x)
         sage: sgn(x)._fricas_init_()                                                    # needs sage.symbolic
         '(x+->abs(x)/x)(x)'
-        sage: sgn(x)._giac_()                                                           # needs sage.libs.giac sage.symbolic
+        sage: sgn(x)._giac_()                                                           # needs giac sage.symbolic
         sign(sageVARx)
 
     Test for :issue:`31085`::

src/sage/functions/other.py

@@ -1860,7 +1860,7 @@ def __init__(self):
             sage: isinstance(r.operator(),      # known bug                             # needs sympy
             ....:     sage.functions.other.Function_prod)
             True
-            sage: giac(sprod(m, m, 1, n)).sage()
+            sage: giac(sprod(m, m, 1, n)).sage()  # needs giac
             factorial(n)
         """
         BuiltinFunction.__init__(self, "product", nargs=4,

src/sage/functions/piecewise.py

@@ -1470,16 +1470,18 @@ def _giac_init_(self, parameters, variable):
 
             EXAMPLES::
 
+                sage: # needs giac
                 sage: ex = piecewise([((0, 1), pi), ([1, 2], x)])
-                sage: f = ex._giac_(); f                                                # needs sage.libs.giac
+                sage: f = ex._giac_(); f
                 piecewise(((sageVARx>0) and (1>sageVARx)),pi,((sageVARx>=1) and (2>=sageVARx)),sageVARx)
-                sage: f.diff(x)                                                         # needs sage.libs.giac
+                sage: f.diff(x)
                 piecewise(((sageVARx>0) and (1>sageVARx)),0,((sageVARx>=1) and (2>=sageVARx)),1)
 
-                sage: ex = piecewise([((-100, -2), 1/x), ((1, +oo), cos(x))])           # needs sage.libs.giac
-                sage: g = ex._giac_(); g                                                # needs sage.libs.giac
+                sage: # needs giac
+                sage: ex = piecewise([((-100, -2), 1/x), ((1, +oo), cos(x))])
+                sage: g = ex._giac_(); g
                 piecewise(((sageVARx>-100) and ((-2)>sageVARx)),1/sageVARx,sageVARx>1,cos(sageVARx))
-                sage: g.diff(x)                                                         # needs sage.libs.giac
+                sage: g.diff(x)
                 piecewise(((sageVARx>-100) and ((-2)>sageVARx)),-1/sageVARx^2,sageVARx>1,-sin(sageVARx))
 
             TESTS::

src/sage/interfaces/giac.py

@@ -1,3 +1,4 @@
+# sage.doctest: needs giac
 r"""
 Pexpect Interface to Giac
 

src/sage/interfaces/interface.py

@@ -275,7 +275,7 @@ def __call__(self, x, name=None):
 
         Check conversion of Booleans (:issue:`28705`)::
 
-            sage: giac(True)
+            sage: giac(True)  # needs giac
             true
             sage: maxima(True)
             true
@@ -343,7 +343,7 @@ def _coerce_impl(self, x, use_special=True):
 
         Check that python type ``complex`` can be converted (:issue:`31775`)::
 
-            sage: giac(complex(I))**2  # should not return `j^2`
+            sage: giac(complex(I))**2  # should not return `j^2`  # needs giac
             -1
         """
         if isinstance(x, bool):
@@ -1193,12 +1193,12 @@ def _repr_(self):
             sage: gap(2)
             2
             sage: x = var('x')
-            sage: giac(x)
+            sage: giac(x)  # needs giac
             sageVARx
-            sage: giac(5)
+            sage: giac(5)  # needs giac
             5
             sage: M = matrix(QQ,2,range(4))
-            sage: giac(M)
+            sage: giac(M)  # needs giac
             [[0,1],[2,3]]
             sage: x = var('x')                  # optional - maple
             sage: maple(x)                      # optional - maple
@@ -1338,7 +1338,7 @@ def __bool__(self):
         By default this returns ``True`` for elements that are considered to be
         not ``False`` by the interface (:issue:`28705`)::
 
-            sage: bool(giac('"a"'))
+            sage: bool(giac('"a"'))  # needs giac
             True
         """
         P = self._check_valid()

src/sage/libs/giac/__init__.py

@@ -1,3 +1,4 @@
+# sage.doctest: needs sage.libs.giac
 """
 Wrappers for Giac functions
 

src/sage/libs/giac/giac.pyx

@@ -1,3 +1,4 @@
+# sage.doctest: needs sage.libs.giac
 # distutils: libraries = giac
 # distutils: language = c++
 # distutils: extra_compile_args = -std=c++11

src/sage/matrix/matrix1.pyx

@@ -216,21 +216,21 @@ cdef class Matrix(Matrix0):
         EXAMPLES::
 
             sage: M = matrix(ZZ, 2, range(4))
-            sage: giac(M)                                                               # needs sage.libs.giac
+            sage: giac(M)                                                               # needs giac
             [[0,1],[2,3]]
 
             sage: M = matrix(QQ, 3, [1,2,3, 4/3,5/3,6/4, 7,8,9])
-            sage: giac(M)                                                               # needs sage.libs.giac
+            sage: giac(M)                                                               # needs giac
             [[1,2,3],[4/3,5/3,3/2],[7,8,9]]
 
             sage: P.<x> = ZZ[]
             sage: M = matrix(P, 2, [-9*x^2-2*x+2, x-1, x^2+8*x, -3*x^2+5])
-            sage: giac(M)                                                               # needs sage.libs.giac
+            sage: giac(M)                                                               # needs giac
             [[-9*sageVARx^2-2*sageVARx+2,sageVARx-1],[sageVARx^2+8*sageVARx,-3*sageVARx^2+5]]
 
             sage: y = var('y')                                                          # needs sage.symbolic
             sage: M = matrix(SR, 2, [y+sin(y), y - 4, 1/y, dilog(y)])                   # needs sage.symbolic
-            sage: giac(M).det().sage()                                                  # needs sage.libs.giac sage.symbolic
+            sage: giac(M).det().sage()                                                  # needs giac sage.symbolic
             (y^2*dilog(y) + y*dilog(y)*sin(y) - y + 4)/y
         """
         s = ','.join('[' + ','.join(cf._giac_init_() for cf in row) + ']'

src/sage/modules/free_module_element.pyx

@@ -1007,20 +1007,20 @@ cdef class FreeModuleElement(Vector):   # abstract base class
         EXAMPLES::
 
             sage: v = vector(ZZ, 4, range(4))
-            sage: giac(v) + v                                                           # needs sage.libs.giac
+            sage: giac(v) + v                                                           # needs giac
             [0,2,4,6]
 
         ::
 
             sage: v = vector(QQ, 3, [2/3, 0, 5/4])
-            sage: giac(v)                                                               # needs sage.libs.giac
+            sage: giac(v)                                                               # needs giac
             [2/3,0,5/4]
 
         ::
 
             sage: P.<x> = ZZ[]
             sage: v = vector(P, 3, [x^2 + 2, 2*x + 1, -2*x^2 + 4*x])
-            sage: giac(v)                                                               # needs sage.libs.giac
+            sage: giac(v)                                                               # needs giac
             [sageVARx^2+2,2*sageVARx+1,-2*sageVARx^2+4*sageVARx]
         """
         return self.list()

src/sage/rings/polynomial/multi_polynomial.pyx

@@ -1114,7 +1114,7 @@ cdef class MPolynomial(CommutativePolynomial):
 
         TESTS::
 
-            sage: # needs sage.libs.giac
+            sage: # needs giac
             sage: R.<x,y,z> = GF(101)['e,i'][]
             sage: f = R('e*i') * x + y^2
             sage: f._giac_init_()