sagemathgh-37993: sage.calculus.expr: Split out from `sage.calculus…

….all`

    
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Cherry-picked from sagemath#36676/sagemath#37900.

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- [ ] I have created tests covering the changes.
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preview.

### ⌛ Dependencies

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URL: sagemath#37993
Reported by: Matthias Köppe
Reviewer(s): John H. Palmieri, Matthias Köppe

src/doc/en/reference/calculus/index.rst

@@ -23,6 +23,7 @@ Using calculus
 
 - :doc:`More about symbolic variables and functions <sage/calculus/var>`
 - :doc:`Main operations on symbolic expressions <sage/symbolic/expression>`
+- :doc:`sage/calculus/expr`
 - :doc:`Assumptions about symbols and functions <sage/symbolic/assumptions>`
 - :doc:`sage/symbolic/relation`
 - :doc:`sage/symbolic/integration/integral`
@@ -65,6 +66,7 @@ Internal functionality supporting calculus
 
    sage/symbolic/expression
    sage/symbolic/callable
+   sage/calculus/expr
    sage/symbolic/assumptions
    sage/symbolic/relation
    sage/calculus/calculus

src/sage/calculus/all.py

@@ -21,7 +21,8 @@
                         eulers_method_2x2_plot, desolve_rk4, desolve_system_rk4,
                         desolve_odeint, desolve_mintides, desolve_tides_mpfr)
 
-from .var import (var, function, clear_vars)
+from sage.calculus.expr import symbolic_expression
+from sage.calculus.var import (var, function, clear_vars)
 
 from .transforms.all import *
 
@@ -30,204 +31,4 @@
 lazy_import("sage.calculus.riemann", ["Riemann_Map"])
 lazy_import("sage.calculus.interpolators", ["polygon_spline", "complex_cubic_spline"])
 
-from sage.modules.free_module_element import vector
-from sage.matrix.constructor import matrix
-
-
-def symbolic_expression(x):
-    """
-    Create a symbolic expression or vector of symbolic expressions from x.
-
-    INPUT:
-
-    - ``x`` - an object
-
-    OUTPUT:
-
-    - a symbolic expression.
-
-    EXAMPLES::
-
-        sage: a = symbolic_expression(3/2); a
-        3/2
-        sage: type(a)
-        <class 'sage.symbolic.expression.Expression'>
-        sage: R.<x> = QQ[]; type(x)
-        <class 'sage.rings.polynomial.polynomial_rational_flint.Polynomial_rational_flint'>
-        sage: a = symbolic_expression(2*x^2 + 3); a
-        2*x^2 + 3
-        sage: type(a)
-        <class 'sage.symbolic.expression.Expression'>
-        sage: from sage.structure.element import Expression
-        sage: isinstance(a, Expression)
-        True
-        sage: a in SR
-        True
-        sage: a.parent()
-        Symbolic Ring
-
-    Note that equations exist in the symbolic ring::
-
-        sage: E = EllipticCurve('15a'); E
-        Elliptic Curve defined by y^2 + x*y + y = x^3 + x^2 - 10*x - 10 over Rational Field
-        sage: symbolic_expression(E)
-        x*y + y^2 + y == x^3 + x^2 - 10*x - 10
-        sage: symbolic_expression(E) in SR
-        True
-
-    If ``x`` is a list or tuple, create a vector of symbolic expressions::
-
-        sage: v = symbolic_expression([x,1]); v
-        (x, 1)
-        sage: v.base_ring()
-        Symbolic Ring
-        sage: v = symbolic_expression((x,1)); v
-        (x, 1)
-        sage: v.base_ring()
-        Symbolic Ring
-        sage: v = symbolic_expression((3,1)); v
-        (3, 1)
-        sage: v.base_ring()
-        Symbolic Ring
-        sage: E = EllipticCurve('15a'); E
-        Elliptic Curve defined by y^2 + x*y + y = x^3 + x^2 - 10*x - 10 over Rational Field
-        sage: v = symbolic_expression([E,E]); v
-        (x*y + y^2 + y == x^3 + x^2 - 10*x - 10, x*y + y^2 + y == x^3 + x^2 - 10*x - 10)
-        sage: v.base_ring()
-        Symbolic Ring
-
-    Likewise, if ``x`` is a vector, create a vector of symbolic expressions::
-
-        sage: u = vector([1, 2, 3])
-        sage: v = symbolic_expression(u); v
-        (1, 2, 3)
-        sage: v.parent()
-        Vector space of dimension 3 over Symbolic Ring
-
-    If ``x`` is a list or tuple of lists/tuples/vectors, create a matrix of symbolic expressions::
-
-        sage: M = symbolic_expression([[1, x, x^2], (x, x^2, x^3), vector([x^2, x^3, x^4])]); M
-        [  1   x x^2]
-        [  x x^2 x^3]
-        [x^2 x^3 x^4]
-        sage: M.parent()
-        Full MatrixSpace of 3 by 3 dense matrices over Symbolic Ring
-
-    If ``x`` is a matrix, create a matrix of symbolic expressions::
-
-        sage: A = matrix([[1, 2, 3], [4, 5, 6]])
-        sage: B = symbolic_expression(A); B
-        [1 2 3]
-        [4 5 6]
-        sage: B.parent()
-        Full MatrixSpace of 2 by 3 dense matrices over Symbolic Ring
-
-    If ``x`` is a function, for example defined by a ``lambda`` expression, create a
-    symbolic function::
-
-        sage: f = symbolic_expression(lambda z: z^2 + 1); f
-        z |--> z^2 + 1
-        sage: f.parent()
-        Callable function ring with argument z
-        sage: f(7)
-        50
-
-    If ``x`` is a list or tuple of functions, or if ``x`` is a function that returns a list
-    or tuple, create a callable symbolic vector::
-
-        sage: symbolic_expression([lambda mu, nu: mu^2 + nu^2, lambda mu, nu: mu^2 - nu^2])
-        (mu, nu) |--> (mu^2 + nu^2, mu^2 - nu^2)
-        sage: f = symbolic_expression(lambda uwu: [1, uwu, uwu^2]); f
-        uwu |--> (1, uwu, uwu^2)
-        sage: f.parent()
-        Vector space of dimension 3 over Callable function ring with argument uwu
-        sage: f(5)
-        (1, 5, 25)
-        sage: f(5).parent()
-        Vector space of dimension 3 over Symbolic Ring
-
-    TESTS:
-
-    Lists, tuples, and vectors of length 0 become vectors over a symbolic ring::
-
-        sage: symbolic_expression([]).parent()
-        Vector space of dimension 0 over Symbolic Ring
-        sage: symbolic_expression(()).parent()
-        Vector space of dimension 0 over Symbolic Ring
-        sage: symbolic_expression(vector(QQ, 0)).parent()
-        Vector space of dimension 0 over Symbolic Ring
-
-    If a matrix has dimension 0, the result is still a matrix over a symbolic ring::
-
-        sage: symbolic_expression(matrix(QQ, 2, 0)).parent()
-        Full MatrixSpace of 2 by 0 dense matrices over Symbolic Ring
-        sage: symbolic_expression(matrix(QQ, 0, 3)).parent()
-        Full MatrixSpace of 0 by 3 dense matrices over Symbolic Ring
-
-    Also functions defined using ``def`` can be used, but we do not advertise it as a use case::
-
-        sage: def sos(x, y):
-        ....:     return x^2 + y^2
-        sage: symbolic_expression(sos)
-        (x, y) |--> x^2 + y^2
-
-    Functions that take a varying number of arguments or keyword-only arguments are not accepted::
-
-        sage: def variadic(x, *y):
-        ....:     return x
-        sage: symbolic_expression(variadic)
-        Traceback (most recent call last):
-        ...
-        TypeError: unable to convert <function variadic at 0x...> to a symbolic expression
-
-        sage: def function_with_keyword_only_arg(x, *, sign=1):
-        ....:     return sign * x
-        sage: symbolic_expression(function_with_keyword_only_arg)
-        Traceback (most recent call last):
-        ...
-        TypeError: unable to convert <function function_with_keyword_only_arg at 0x...>
-        to a symbolic expression
-    """
-    from sage.symbolic.expression import Expression
-    from sage.symbolic.ring import SR
-    from sage.modules.free_module_element import is_FreeModuleElement
-    from sage.structure.element import is_Matrix
-
-    if isinstance(x, Expression):
-        return x
-    elif hasattr(x, '_symbolic_'):
-        return x._symbolic_(SR)
-    elif isinstance(x, (tuple, list)) or is_FreeModuleElement(x):
-        expressions = [symbolic_expression(item) for item in x]
-        if not expressions:
-            # Make sure it is symbolic also when length is 0
-            return vector(SR, 0)
-        if is_FreeModuleElement(expressions[0]):
-            return matrix(expressions)
-        return vector(expressions)
-    elif is_Matrix(x):
-        if not x.nrows() or not x.ncols():
-            # Make sure it is symbolic and of correct dimensions
-            # also when a matrix dimension is 0
-            return matrix(SR, x.nrows(), x.ncols())
-        rows = [symbolic_expression(row) for row in x.rows()]
-        return matrix(rows)
-    elif callable(x):
-        from inspect import signature, Parameter
-        try:
-            s = signature(x)
-        except ValueError:
-            pass
-        else:
-            if all(param.kind in (Parameter.POSITIONAL_ONLY, Parameter.POSITIONAL_OR_KEYWORD)
-                   for param in s.parameters.values()):
-                vars = [SR.var(name) for name in s.parameters.keys()]
-                result = x(*vars)
-                if isinstance(result, (tuple, list)):
-                    return vector(SR, result).function(*vars)
-                else:
-                    return SR(result).function(*vars)
-    return SR(x)
-
-
 from . import desolvers