Make Drop[] of 0th not error, DRY "normal" error messages, and go o…

…ver `Drop` doc (#1225)

* Make `Drop[]` of  0th not error 
* DRY "normal" error messages
* Go over `Drop` doc
* Move some doctests to pytests when they belong there
* Move some pytests to less generic and more the more specific module
that the test tests

Fixes #1223

mathics/builtin/assignments/assignment.py

@@ -355,10 +355,6 @@ class UpSet(InfixOperator, _SetOperator):
     >> UpValues[b]
      = {HoldPattern[a[b]] :> 3}
 
-    >> a ^= 3
-     : Nonatomic expression expected.
-     = 3
-
     You can use 'UpSet' to specify special values like format values.
     However, these values will not be saved in 'UpValues':
     >> Format[r] ^= "custom";

mathics/builtin/atomic/symbols.py

@@ -11,7 +11,7 @@
 from mathics_scanner.tokeniser import is_symbol_name
 
 from mathics.core.assignment import get_symbol_values
-from mathics.core.atoms import String
+from mathics.core.atoms import Integer1, String
 from mathics.core.attributes import (
     A_HOLD_ALL,
     A_HOLD_FIRST,
@@ -39,6 +39,7 @@
 )
 from mathics.core.systemsymbols import (
     SymbolAttributes,
+    SymbolContext,
     SymbolDefinition,
     SymbolFormat,
     SymbolGrid,
@@ -122,7 +123,9 @@ def eval(self, symbol, evaluation):
 
         name = symbol.get_name()
         if not name:
-            evaluation.message("Context", "normal")
+            evaluation.message(
+                "Context", "normal", Integer1, Expression(SymbolContext, symbol)
+            )
             return
         assert "`" in name
         context = name[: name.rindex("`") + 1]

mathics/builtin/exp_structure/general.py

@@ -3,14 +3,14 @@
 Structural Expression Functions
 """
 
-from mathics.core.atoms import Integer
+from mathics.core.atoms import Integer, Integer1
 from mathics.core.builtin import Builtin, InfixOperator, Predefined
 from mathics.core.exceptions import InvalidLevelspecError
 from mathics.core.expression import Evaluation, Expression
 from mathics.core.list import ListExpression
 from mathics.core.rules import BasePattern
 from mathics.core.symbols import Atom, SymbolFalse, SymbolTrue
-from mathics.core.systemsymbols import SymbolMap
+from mathics.core.systemsymbols import SymbolMap, SymbolSortBy
 from mathics.eval.parts import python_levelspec, walk_levels
 
 
@@ -265,7 +265,9 @@ def eval(self, li, f, evaluation: Evaluation):
         "SortBy[li_, f_]"
 
         if isinstance(li, Atom):
-            evaluation.message("Sort", "normal")
+            evaluation.message(
+                "Sort", "normal", Integer1, Expression(SymbolSortBy, li, f)
+            )
             return
         elif li.get_head_name() != "System`List":
             expr = Expression(SymbolSortBy, li, f)

mathics/builtin/intfns/combinatorial.py

@@ -14,7 +14,7 @@
 
 from itertools import combinations
 
-from mathics.core.atoms import Integer
+from mathics.core.atoms import Integer, Integer1
 from mathics.core.attributes import (
     A_LISTABLE,
     A_N_HOLD_FIRST,
@@ -536,7 +536,6 @@ class Subsets(Builtin):
 
     messages = {
         "nninfseq": "Position 2 of `1` must be All, Infinity, a non-negative integer, or a List whose first element (required) is a non-negative integer, second element (optional) is a non-negative integer or Infinity, and third element (optional) is a nonzero integer.",
-        "normal": "Nonatomic expression expected at position 1 in `1`.",
     }
 
     rules = {
@@ -549,7 +548,9 @@ def eval_list(self, list, evaluation):
         "Subsets[list_]"
 
         if isinstance(list, Atom):
-            evaluation.message("Subsets", "normal", Expression(SymbolSubsets, list))
+            evaluation.message(
+                "Subsets", "normal", Integer1, Expression(SymbolSubsets, list)
+            )
         else:
             return self.eval_list_n(list, Integer(len(list.elements)), evaluation)
 
@@ -558,7 +559,7 @@ def eval_list_n(self, list, n, evaluation):
 
         expr = Expression(SymbolSubsets, list, n)
         if isinstance(list, Atom):
-            evaluation.message("Subsets", "normal", expr)
+            evaluation.message("Subsets", "normal", Integer1, expr)
             return
         else:
             head_t = list.head
@@ -584,7 +585,7 @@ def eval_list_pattern(self, list, n, evaluation):
         expr = Expression(SymbolSubsets, list, n)
 
         if isinstance(list, Atom):
-            evaluation.message("Subsets", "normal", expr)
+            evaluation.message("Subsets", "normal", Integer1, expr)
             return
         else:
             head_t = list.head
@@ -663,7 +664,7 @@ def eval_atom_pattern(self, list, n, spec, evaluation):
         "Subsets[list_?AtomQ, Pattern[n,_List|All|DirectedInfinity[1]], spec_]"
 
         evaluation.message(
-            "Subsets", "normal", Expression(SymbolSubsets, list, n, spec)
+            "Subsets", "normal", Integer1, Expression(SymbolSubsets, list, n, spec)
         )
 
 

mathics/builtin/layout.py

@@ -179,9 +179,6 @@ class Infix(Builtin):
      = a + b - c
     """
 
-    messages = {
-        "normal": "Nonatomic expression expected at position `1`",
-    }
     summary_text = "infix form"
 
 

mathics/builtin/list/constructing.py

@@ -13,7 +13,7 @@
 from typing import Optional, Tuple
 
 from mathics.builtin.box.layout import RowBox
-from mathics.core.atoms import Integer, is_integer_rational_or_real
+from mathics.core.atoms import Integer, Integer1, is_integer_rational_or_real
 from mathics.core.attributes import A_HOLD_FIRST, A_LISTABLE, A_LOCKED, A_PROTECTED
 from mathics.core.builtin import BasePattern, Builtin, IterationFunction
 from mathics.core.convert.expression import to_expression
@@ -23,7 +23,7 @@
 from mathics.core.expression import Expression, structure
 from mathics.core.list import ListExpression
 from mathics.core.symbols import Atom, Symbol
-from mathics.core.systemsymbols import SymbolNormal
+from mathics.core.systemsymbols import SymbolNormal, SymbolTuples
 from mathics.eval.lists import get_tuples, list_boxes
 
 
@@ -607,7 +607,7 @@ def eval_n(self, expr, n: Integer, evaluation: Evaluation):
         "Tuples[expr_, n_Integer]"
 
         if isinstance(expr, Atom):
-            evaluation.message("Tuples", "normal")
+            evaluation.message("Tuples", "normal", Integer1, Expression(expr, n))
             return
         py_n = n.value
         if py_n is None or py_n < 0:
@@ -633,10 +633,12 @@ def eval_lists(self, exprs, evaluation: Evaluation):
 
         exprs = exprs.get_sequence()
         items = []
-        for expr in exprs:
+        for i, expr in enumerate(exprs):
             evaluation.check_stopped()
             if isinstance(expr, Atom):
-                evaluation.message("Tuples", "normal")
+                evaluation.message(
+                    "Tuples", "normal", Integer(i + 1), Expression(SymbolTuples)
+                )
                 return
             items.append(expr.elements)