remove _target

src/sage/data_structures/stream.py

@@ -1011,32 +1011,14 @@ def __init__(self, approximate_order, true_order=False):
             sage: C = Stream_uninitialized(0)
             sage: TestSuite(C).run(skip="_test_pickling")
         """
-        self._target = None
         if approximate_order is None:
             raise ValueError("the valuation must be specified for undefined series")
         super().__init__(False, true_order)
+        self._iter = None
         self._approximate_order = approximate_order
 
-    def iterate_coefficients(self):
-        """
-        A generator for the coefficients of ``self``.
-
-        EXAMPLES::
-
-            sage: from sage.data_structures.stream import Stream_uninitialized
-            sage: from sage.data_structures.stream import Stream_exact
-            sage: z = Stream_exact([1], order=1)
-            sage: C = Stream_uninitialized(0)
-            sage: C._target
-            sage: C._target = z
-            sage: n = C.iterate_coefficients()
-            sage: [next(n) for _ in range(10)]
-            [0, 1, 0, 0, 0, 0, 0, 0, 0, 0]
-        """
-        n = self._approximate_order
-        while True:
-            yield self._target[n]
-            n += 1
+    def define(self, coeff_stream):
+        self._iter = coeff_stream.iterate_coefficients()
 
 
 class Stream_unary(Stream_inexact):

src/sage/rings/lazy_series.py

@@ -938,12 +938,7 @@ def __bool__(self):
         if isinstance(self._coeff_stream, Stream_exact):
             return True
         if isinstance(self._coeff_stream, Stream_uninitialized):
-            if self._coeff_stream._target is None:
-                return True
-            if isinstance(self._coeff_stream._target, Stream_zero):
-                return False
-            if isinstance(self._coeff_stream._target, Stream_exact):
-                return True
+            return True
         if self._coeff_stream._is_sparse:
             cache = self._coeff_stream._cache
             if any(cache[a] for a in cache):
@@ -1207,7 +1202,7 @@ def define(self, s):
             O^7
 
         """
-        if not isinstance(self._coeff_stream, Stream_uninitialized) or self._coeff_stream._target is not None:
+        if not isinstance(self._coeff_stream, Stream_uninitialized) or self._coeff_stream._iter is not None:
             raise ValueError("series already defined")
 
         if not isinstance(s, LazyModuleElement):
@@ -1219,7 +1214,7 @@ def define(self, s):
             self._coeff_stream = coeff_stream
             return
 
-        self._coeff_stream._target = coeff_stream
+        self._coeff_stream.define(coeff_stream)
 
     # an alias for compatibility with padics
     set = define
@@ -1266,7 +1261,7 @@ def _repr_(self):
         """
         if isinstance(self._coeff_stream, Stream_zero):
             return '0'
-        if isinstance(self._coeff_stream, Stream_uninitialized) and self._coeff_stream._target is None:
+        if isinstance(self._coeff_stream, Stream_uninitialized) and self._coeff_stream._iter is None:
             return 'Uninitialized Lazy Laurent Series'
         return self._format_series(repr)
 
@@ -1316,7 +1311,7 @@ def _latex_(self):
         from sage.misc.latex import latex
         if isinstance(self._coeff_stream, Stream_zero):
             return latex('0')
-        if isinstance(self._coeff_stream, Stream_uninitialized) and self._coeff_stream._target is None:
+        if isinstance(self._coeff_stream, Stream_uninitialized) and self._coeff_stream._iter is None:
             return latex("Undef")
         return self._format_series(latex)
 
@@ -1336,7 +1331,7 @@ def _ascii_art_(self):
         from sage.typeset.ascii_art import ascii_art, AsciiArt
         if isinstance(self._coeff_stream, Stream_zero):
             return AsciiArt('0')
-        if isinstance(self._coeff_stream, Stream_uninitialized) and self._coeff_stream._target is None:
+        if isinstance(self._coeff_stream, Stream_uninitialized) and self._coeff_stream._iter is None:
             return AsciiArt('Uninitialized Lazy Laurent Series')
         return self._format_series(ascii_art, True)
 
@@ -1356,7 +1351,7 @@ def _unicode_art_(self):
         from sage.typeset.unicode_art import unicode_art, UnicodeArt
         if isinstance(self._coeff_stream, Stream_zero):
             return UnicodeArt('0')
-        if isinstance(self._coeff_stream, Stream_uninitialized) and self._coeff_stream._target is None:
+        if isinstance(self._coeff_stream, Stream_uninitialized) and self._coeff_stream._iter is None:
             return UnicodeArt('Uninitialized Lazy Laurent Series')
         return self._format_series(unicode_art, True)
 
@@ -3145,7 +3140,7 @@ def exp(self):
         d_self_f = Stream_cauchy_mul(d_self, f._coeff_stream, False)
         int_d_self_f = Stream_function(lambda n: d_self_f[n-1] / R(n) if n else R.one(),
                                        False, 0)
-        f._coeff_stream._target = int_d_self_f
+        f._coeff_stream.define(int_d_self_f)
         return f
 
     def log(self):