1f39d4148e
The purpose of this class is much like Emacs' (interactive) form: it
allows a value expression function to declare exactly how many
arguments, and of what type, it intends to receive. It then offers
type-safe access to theese arguments in a consistent manner.
An example value expression function definition in C++:
value_t fn_foo(call_scope_t& scope) {
// We expect a string, an integer, and an optional date
interactive_t args(scope, "sl&d");
std::cout << "String = " << args.get<string>(0)
<< "Integer = " << args.get<long>(1) << std::endl;
if (args.has(2)) // was a date provided?
std::cout << "Date = " << args.get<date_t>(2) << std::endl;
return NULL_VALUE;
}
There is also an in_context_t<T> template, which finds the context type
T in the current scope hierarchy. The in_context_t then also acts as a
smart pointer to reference this context object, in addition to serving
the same duty as interactive_t. This combination of intent is solely
for the sake of brevity.
value_t fn_bar(call_scope_t& scope) {
in_context_t<account_t> env(scope, "sl&d");
std::cout << "Account name = " << env->fullname()
<< "String arg = " << env.get<string>(0)
<< std::endl;
return NULL_VALUE;
}
As you can see here, 'env' acts as a smart pointer to the required
context, and an object to extract the typed arguments.
63 lines
2.4 KiB
C++
63 lines
2.4 KiB
C++
/*
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* Copyright (c) 2003-2009, John Wiegley. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* - Neither the name of New Artisans LLC nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "scope.h"
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namespace ledger {
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void symbol_scope_t::define(const string& name, expr_t::ptr_op_t def)
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{
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DEBUG("scope.symbols", "Defining '" << name << "' = " << def);
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std::pair<symbol_map::iterator, bool> result
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= symbols.insert(symbol_map::value_type(name, def));
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if (! result.second) {
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symbol_map::iterator i = symbols.find(name);
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assert(i != symbols.end());
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symbols.erase(i);
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std::pair<symbol_map::iterator, bool> result2
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= symbols.insert(symbol_map::value_type(name, def));
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if (! result2.second)
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throw_(compile_error, "Redefinition of '" << name << "' in same scope");
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}
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}
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expr_t::ptr_op_t symbol_scope_t::lookup(const string& name)
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{
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symbol_map::const_iterator i = symbols.find(name);
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if (i != symbols.end())
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return (*i).second;
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return child_scope_t::lookup(name);
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}
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} // namespace ledger
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