1/p bounds added

src/nmreval/fit/parameter.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import ast
 import re
 from itertools import count
 from io import StringIO
@@ -39,10 +40,11 @@ class Parameters(dict):
             value: str | float | int = None,
             *,
             var: bool = True,
-            lb: float = -np.inf, ub: float = np.inf) -> Parameter:
+            lb: str | float = -np.inf,
+            ub: str | float = np.inf) -> Parameter:
 
         par = Parameter(name=name, value=value, var=var, lb=lb, ub=ub)
-        key = f'p{next(Parameters.parameter_counter)}'
+        key = f'_p{next(Parameters.parameter_counter)}'
 
         self.add_parameter(key, par)
 
@@ -99,6 +101,91 @@ class Parameters(dict):
 
                 p._expr = expression
 
+    def prepare_bounds(self):
+        original_values = list(self.values())
+        for param in original_values:
+            already_with_expression = False
+            for mode, value in (('lower', param.lb), ('upper', param.ub)):
+                if already_with_expression:
+                    raise ValueError('Only one boundary can be an expression')
+                already_with_expression = self.parse(param, value, bnd=mode)
+
+    def parse(self, parameter, expression: str, bnd: str = 'lower') -> bool:
+        try:
+            float(expression)
+            return False
+
+        except ValueError:
+            pp = ast.parse(expression)
+            expr_syms = pp.body[0].value
+
+            if isinstance(expr_syms, ast.BinOp):
+                left, op, right = expr_syms.left, expr_syms.op, expr_syms.right
+
+                # check for sign in numerator
+                sign = 1
+                if isinstance(left, ast.UnaryOp):
+                    if isinstance(left.op, (ast.Not, ast.Invert)):
+                        raise ValueError('Only `+` and `-` are supported for signs')
+                    if isinstance(left.op, ast.USub):
+                        sign = -1
+                    left = left.operand
+
+                # is expression number / parameter?
+                if not (isinstance(left, ast.Constant) and isinstance(op, ast.Div) and isinstance(right, ast.Name)):
+                    raise ValueError('Only simple division `const/parameter` are possible')
+
+                result = self.make_proxy_div(parameter, left.value*sign, right.id, bnd=bnd)
+
+                return result
+
+            else:
+                raise ValueError('I cannot work under these conditions')
+
+    def make_proxy_div(self, param, num: str | float, denom: str | float, bnd: str = 'upper') -> bool:
+        other_param = self[denom]
+        other_lb, other_ub = other_param.lb, other_param.ub
+
+        proxy = {'name': f'{param.name}*{other_param.name}', 'value': other_param.value*param.value, 'lb': None, 'ub': None}
+
+        # switching signs is bad for inequalities
+        if other_lb < 0 < other_ub:
+            raise ValueError('Parameter in expression changes sign')
+
+        if bnd == 'upper':
+            # this whole schlamassel is only working for some values as lower bound
+            if param.lb not in [-np.inf, 0]:
+                raise ValueError('Invalid lower bounds')
+
+            if other_ub < 0 or num < 0:
+                # upper bound is always negative, switch boundaries
+                proxy['lb'] = num
+                proxy['ub'] = param.lb if param.lb == 0 else np.inf
+            else:
+                # upper bound is always positive
+                proxy['lb'] = param.lb
+                proxy['ub'] = num
+
+        elif bnd == 'lower':
+            if param.ub not in [np.inf, 0]:
+                raise ValueError('Invalid upper bound')
+
+            if other_ub <= 0 or num < 0:
+                proxy['lb'] = param.lb if param.lb == 0 else np.inf
+                proxy['ub'] = num
+            else:
+                proxy['lb'] = num
+                proxy['ub'] = param.ub
+
+        else:
+            raise ValueError(f'unknown bound {bnd!r}, use `upper`or `lower`')
+
+        param.set_expression(f'{num}/{denom}')
+        self.add(**proxy)
+        self.update_namespace()
+
+        return True
+
 
 class Parameter:
     """
@@ -106,15 +193,21 @@ class Parameter:
     """
 
     # TODO Parameter should know its own key
-    def __init__(self, name: str, value: float | str, var: bool = True, lb: float = -np.inf, ub: float = np.inf):
+    def __init__(self,
+                 name: str,
+                 value: float | str,
+                 var: bool = True,
+                 lb: str | float = -np.inf,
+                 ub: str | float = np.inf,
+                 ):
         self._value: float | None = None
         self.var: bool = bool(var) if var is not None else True
         self.error:  None | float = None if self.var is False else 0.0
         self.name: str = name
         self.function: str = ""
 
-        self.lb: None | float = lb if lb is not None else -np.inf
-        self.ub: float | None = ub if ub is not None else np.inf
+        self.lb: str | None | float = lb if lb is not None else -np.inf
+        self.ub: str | float | None = ub if ub is not None else np.inf
         self.namespace: dict = {}
         self.eval_allowed: bool = True
         self._expr: None | str = None
@@ -126,10 +219,13 @@ class Parameter:
             self._expr = value
             self.var = False
         else:
+            if isinstance(self.lb, (int, float)) and isinstance(self.ub, (int, float)):
                 if self.lb <= value <= self.ub:
                     self._value = value
                 else:
                     raise ValueError('Value of parameter is outside bounds')
+            else:
+                self._value = value
 
             self.init_val = value
 
@@ -191,6 +287,12 @@ class Parameter:
 
         return
 
+    def set_expression(self, expr: str):
+        self._value = None
+        self._expr_disp = expr
+        self._expr = expr
+        self.var = False
+
     @property
     def scaled_error(self) -> None | float:
         if self.error is not None: