feat: Add new flag ? to EVAL tag, used to hide implicit 1 when mu…

…ltiplying.

ptyx/latex_generator.py

@@ -399,9 +399,10 @@ def _parse_EVAL_tag(self, node: Node):
                 self.flags["round"] = int(arg)
             elif arg == ".":
                 self.flags["."] = True
+            elif arg == "?":
+                self.flags["?"] = True
             elif arg in ("floats", "float"):
                 self.flags["floats"] = True
-
             elif arg == "str":
                 self.flags["str"] = True
             else:
@@ -735,6 +736,7 @@ def _eval_and_format_python_expr(self, code: str) -> str:
             code = code.rstrip(";")
             display_result = False
 
+        result = ""
         for subcode in advanced_split(code, ";", brackets=()):
             result = self._eval_python_expr(subcode)
         # Note that only last result will be displayed.
@@ -745,15 +747,23 @@ def _eval_and_format_python_expr(self, code: str) -> str:
         if not display_result:
             return ""
 
+        if flags.get("?"):
+            if result == 1:
+                if flags.get("+"):
+                    return "+"
+                return ""
+            elif result == -1:
+                result = "-"
+
         if sympy_code and not flags.get("str"):
             from ptyx.printers import sympy2latex
 
             latex = sympy2latex(result, **flags)
         else:
             latex = str(result)
 
-        def neg(latex):
-            return latex.lstrip().startswith("-")
+        def neg(latex_):
+            return latex_.lstrip().startswith("-")
 
         if flags.get("+"):
             if result == 0:

tests/test_tags.py

@@ -219,6 +219,20 @@ def test_ADD():
     assert latex == result
 
 
+def test_EVAL_1():
+    test = r"""
+    #PYTHON
+    a = 1
+    b = 1
+    c = -1
+    #END
+    $#[?]a x #+ #[?]b y #+ #[?]c z = 0$"""
+    target = "$x+y-z=0$" ""
+    c = Compiler()
+    latex = c.parse(code=test)
+    assert latex.replace(" ", "").strip() == target
+
+
 def test_INCLUDE():
     os.chdir(TEST_DIR)
     test = "#SEED{99}First, $a=#{a=7}$#INCLUDE{include_example.txt}Last, $a=#a$ still."