/// <summary>
/// Create or update a named variable to a value.
/// </summary>
/// <param name="name">variable name. This can be used in other formulas.</param>
/// <param name="value">constant value.</param>
public void UpdateVariable(string name, FormulaValue value)
{
var x = value;
if (Formulas.TryGetValue(name, out var fi))
{
// Type should match?
if (fi._type != x.Type)
{
throw new NotSupportedException($"Can't change '{name}''s type from {fi._type} to {x.Type}.");
}
fi._value = x;
// Be sure to preserve used-by set.
}
else
{
Formulas[name] = new RecalcFormulaInfo {
_value = x, _type = x.IRContext.ResultType
};
}
// Could trigger recalcs?
Recalc(name);
}
/// <summary>
/// Create a formula that will be recalculated when its dependent values change.
/// </summary>
/// <param name="name">name of formula. This can be used in other formulas.</param>
/// <param name="expr">expression.</param>
/// <param name="onUpdate">Callback to fire when this value is updated.</param>
public void SetFormula(string name, FormulaWithParameters expr, Action <string, FormulaValue> onUpdate)
{
if (Formulas.ContainsKey(name))
{
throw new InvalidOperationException($"Can't change existing formula: {name}");
}
var check = Check(expr._expression, expr._schema);
check.ThrowOnErrors();
var binding = check._binding;
// We can't have cycles because:
// - formulas can only refer to already-defined values
// - formulas can't be redefined.
HashSet <string> dependsOn = check.TopLevelIdentifiers;
var type = FormulaType.Build(binding.ResultType);
var info = new RecalcFormulaInfo
{
_dependsOn = dependsOn,
_type = type,
_binding = binding,
_onUpdate = onUpdate
};
Formulas[name] = info;
foreach (var x in dependsOn)
{
Formulas[x]._usedBy.Add(name);
}
Recalc(name);
}