stack: Do not save stack in plot, integration or solver

Make sure that `Undo` and `LastArg` work correctly for plotting
functions, integration and solver.

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

src/integrate.cc

@@ -104,6 +104,9 @@ algebraic_p integrate(program_g   eq,
 //   At each step, the size of C is one more than P.
 //   In the implementation below, those arrays are on the stack, P above C.
 {
+    // We will run commands below, do not save stack while doing it
+    settings::PrepareForProgramEvaluation wilLRunPrograms;
+
     // Check if the guess is an algebraic or if we need to extract one
     algebraic_g x, dx, dx2;
     algebraic_g y, dy, sy, sy2;

src/plot.cc

@@ -229,7 +229,7 @@ object::result draw_plot(object::id                  kind,
     algebraic_g      y;
     save<symbol_g *> iref(expression::independent,
                           (symbol_g *) &ppar.independent);
-    settings::SaveSetAngleUnits ssau(false); // For asin, acos, atan
+    settings::PrepareForProgramEvaluation wilLRunPrograms;
     if (ui.draw_graphics())
         if (Settings.DrawPlotAxes())
             draw_axes(ppar);

src/settings.h

@@ -244,6 +244,21 @@ public:
 #define SETTING_BITS(Name, Bits, Low, High, Init)       \
     SETTING(Name, Low, High, Init)
 #include "ids.tbl"
+
+    struct PrepareForProgramEvaluation
+    {
+        SaveSaveLastArguments    saveLastArgs;
+        SaveProgramLastArguments saveProgramLastArg;
+        SaveSaveStack            saveLastStack;
+        SaveSetAngleUnits        saveAngleUnits; // For sin, cos, tan
+
+        PrepareForProgramEvaluation()
+            : saveLastArgs(false),
+              saveProgramLastArg(false),
+              saveLastStack(false),
+              saveAngleUnits(false)
+        {}
+    };
 };
 
 

src/solve.cc

@@ -127,6 +127,9 @@ algebraic_p solve(program_g eq, symbol_g name, object_g guess)
     x = lx;
     record(solve, "Initial range %t-%t", +lx, +hx);
 
+    // We will run programs, do not save stack, etc.
+    settings::PrepareForProgramEvaluation wilLRunPrograms;
+
     // Set independent variable
     save<symbol_g *> iref(expression::independent, &name);
     int              prec = Settings.SolverPrecision();