Merge pull request sympy#23646 from oscargus/prefixlatex

Improve LaTeX-printing of Prefix

sympy/physics/units/prefixes.py

@@ -30,7 +30,7 @@ class Prefix(Expr):
     _op_priority = 13.0
     is_commutative = True
 
-    def __new__(cls, name, abbrev, exponent, base=sympify(10)):
+    def __new__(cls, name, abbrev, exponent, base=sympify(10), latex_repr=None):
 
         name = sympify(name)
         abbrev = sympify(abbrev)
@@ -43,6 +43,7 @@ def __new__(cls, name, abbrev, exponent, base=sympify(10)):
         obj._scale_factor = base**exponent
         obj._exponent = exponent
         obj._base = base
+        obj._latex_repr = latex_repr
         return obj
 
     @property
@@ -57,21 +58,26 @@ def abbrev(self):
     def scale_factor(self):
         return self._scale_factor
 
+    def _latex(self, printer):
+        if self._latex_repr is None:
+            return r'\text{%s}' % self._abbrev
+        return self._latex_repr
+
     @property
     def base(self):
         return self._base
 
     def __str__(self):
-        # TODO: add proper printers and tests:
+        return str(self._abbrev)
+
+    def __repr__(self):
         if self.base == 10:
             return "Prefix(%r, %r, %r)" % (
                 str(self.name), str(self.abbrev), self._exponent)
         else:
             return "Prefix(%r, %r, %r, %r)" % (
                 str(self.name), str(self.abbrev), self._exponent, self.base)
 
-    __repr__ = __str__
-
     def __mul__(self, other):
         from sympy.physics.units import Quantity
         if not isinstance(other, (Quantity, Prefix)):
@@ -160,7 +166,7 @@ def prefix_unit(unit, prefixes):
 deci = Prefix('deci', 'd', -1)
 centi = Prefix('centi', 'c', -2)
 milli = Prefix('milli', 'm', -3)
-micro = Prefix('micro', 'mu', -6)
+micro = Prefix('micro', 'mu', -6, latex_repr=r"\mu")
 nano = Prefix('nano', 'n', -9)
 pico = Prefix('pico', 'p', -12)
 femto = Prefix('femto', 'f', -15)

sympy/printing/latex.py

@@ -25,7 +25,7 @@
 
 from mpmath.libmp.libmpf import prec_to_dps, to_str as mlib_to_str
 
-from sympy.utilities.iterables import has_variety
+from sympy.utilities.iterables import has_variety, sift
 
 import re
 
@@ -516,6 +516,7 @@ def _print_Laplacian(self, expr):
 
     def _print_Mul(self, expr: Expr):
         from sympy.physics.units import Quantity
+        from sympy.physics.units.prefixes import Prefix
         from sympy.simplify import fraction
         separator: str = self._settings['mul_symbol_latex']
         numbersep: str = self._settings['mul_symbol_latex_numbers']
@@ -530,26 +531,29 @@ def convert(expr) -> str:
                     args = list(expr.args)
 
                 # If quantities are present append them at the back
-                args = sorted(args, key=lambda x: isinstance(x, Quantity) or
+                units, nonunits = sift(args, lambda x: isinstance(x, (Quantity, Prefix)) or
                               (isinstance(x, Pow) and
-                               isinstance(x.base, Quantity)))
-
-                return convert_args(args)
+                               isinstance(x.base, Quantity)), binary=True)
+                prefixes, units = sift(units, lambda x: isinstance(x, Prefix), binary=True)
+                return convert_args(nonunits + prefixes + units)
 
         def convert_args(args) -> str:
             _tex = last_term_tex = ""
 
             for i, term in enumerate(args):
                 term_tex = self._print(term)
 
-                if self._needs_mul_brackets(term, first=(i == 0),
-                                            last=(i == len(args) - 1)):
-                    term_tex = r"\left(%s\right)" % term_tex
+                if not isinstance(term, (Quantity, Prefix)):
+                    if self._needs_mul_brackets(term, first=(i == 0),
+                                                last=(i == len(args) - 1)):
+                        term_tex = r"\left(%s\right)" % term_tex
 
-                if _between_two_numbers_p[0].search(last_term_tex) and \
+                    if  _between_two_numbers_p[0].search(last_term_tex) and \
                         _between_two_numbers_p[1].match(str(term)):
-                    # between two numbers
-                    _tex += numbersep
+                        # between two numbers
+                        _tex += numbersep
+                    elif _tex:
+                        _tex += separator
                 elif _tex:
                     _tex += separator
 

sympy/printing/tests/test_latex.py

@@ -48,7 +48,7 @@
 from sympy.ntheory.factor_ import (divisor_sigma, primenu, primeomega, reduced_totient, totient, udivisor_sigma)
 from sympy.physics.quantum import Commutator, Operator
 from sympy.physics.quantum.trace import Tr
-from sympy.physics.units import meter, gibibyte, microgram, second
+from sympy.physics.units import meter, gibibyte, gram, microgram, second, milli, micro
 from sympy.polys.domains.integerring import ZZ
 from sympy.polys.fields import field
 from sympy.polys.polytools import Poly
@@ -2983,6 +2983,9 @@ def test_unit_printing():
     assert latex(5*meter) == r'5 \text{m}'
     assert latex(3*gibibyte) == r'3 \text{gibibyte}'
     assert latex(4*microgram/second) == r'\frac{4 \mu\text{g}}{\text{s}}'
+    assert latex(4*micro*gram/second) == r'\frac{4 \mu \text{g}}{\text{s}}'
+    assert latex(5*milli*meter) == r'5 \text{m} \text{m}'
+    assert latex(milli) == r'\text{m}'
 
 
 def test_issue_17092():