/// <summary>
/// Learn tokens which evalutes to the `expected` string.
/// </summary>
/// <param name="input">Input.</param>
/// <param name="expected">Output: the expected string.</param>
/// <returns>Consistent programs.</returns>
private ProgramSet LearnToken(TInput input, string expected)
{
var programs = new List <ProgramNode>();
// Option 1: err token.
if (expected == input.errNode.code)
{
programs.Add(ErrToken());
}
// Option 2: variable token.
input.TryFind(expected).Select(key =>
{
programs.Add(VarToken(key));
});
// Option 3: constant token.
programs.Add(ConstToken(expected));
return(ProgramSet.List(Symbol("token"), programs));
}
public static string ErrToken(TInput input) => input.errNode.code;
public static string VarToken(TInput input, EnvKey key) => input[key];
public static SyntaxNode Var(TInput input, EnvKey key) => input.inputTree.Leaves().Where(l => l.code == input[key]).ArgMin(l => l.depth);
public static SyntaxNode Err(TInput input) => input.errNode;