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C API: Add nix_init_apply

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Thunks are relevant when initializing attrsets and lists, passing
arguments. This is an important way to produce them.
This commit is contained in:
Robert Hensing 2024-04-17 17:41:23 +02:00
parent 05b9dac754
commit ad643cde58
4 changed files with 157 additions and 2 deletions
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2
src/libexpr-c/nix_api_expr.h
View file

@ -93,6 +93,8 @@ nix_err nix_expr_eval_from_string(
* @param[in] arg The argument to pass to the function.
* @param[out] value The result of the function call.
* @return NIX_OK if the function call was successful, an error code otherwise.
* @see nix_init_apply() for a similar function that does not performs the call immediately, but stores it as a thunk.
* Note the different argument order.
*/
nix_err nix_value_call(nix_c_context * context, EvalState * state, Value * fn, Value * arg, Value * value);

13
src/libexpr-c/nix_api_value.cc
View file

@ -404,6 +404,19 @@ nix_err nix_init_null(nix_c_context * context, Value * value)
NIXC_CATCH_ERRS
}
nix_err nix_init_apply(nix_c_context * context, Value * value, Value * fn, Value * arg)
{
if (context)
context->last_err_code = NIX_OK;
try {
auto & v = check_value_not_null(value);
auto & f = check_value_not_null(fn);
auto & a = check_value_not_null(arg);
v.mkApp(&f, &a);
}
NIXC_CATCH_ERRS
}
nix_err nix_init_external(nix_c_context * context, Value * value, ExternalValue * val)
{
if (context)

20
src/libexpr-c/nix_api_value.h
View file

@ -342,8 +342,24 @@ nix_err nix_init_int(nix_c_context * context, Value * value, int64_t i);
* @param[out] value Nix value to modify
* @return error code, NIX_OK on success.
*/
nix_err nix_init_null(nix_c_context * context, Value * value);
/** @brief Set the value to a thunk that will perform a function application when needed.
*
* Thunks may be put into attribute sets and lists to perform some computation lazily; on demand.
* However, note that in some places, a thunk must not be returned, such as in the return value of a PrimOp.
* In such cases, you may use nix_value_call() instead (but note the different argument order).
*
* @param[out] context Optional, stores error information
* @param[out] value Nix value to modify
* @param[in] fn function to call
* @param[in] arg argument to pass
* @return error code, NIX_OK on successful initialization.
* @see nix_value_call() for a similar function that performs the call immediately and only stores the return value.
* Note the different argument order.
*/
nix_err nix_init_apply(nix_c_context * context, Value * value, Value * fn, Value * arg);
/** @brief Set an external value
* @param[out] context Optional, stores error information
* @param[out] value Nix value to modify
@ -421,7 +437,7 @@ BindingsBuilder * nix_make_bindings_builder(nix_c_context * context, EvalState *
/** @brief Insert bindings into a builder
* @param[out] context Optional, stores error information
* @param[in] builder BindingsBuilder to insert into
* @param[in] name attribute name, copied into the symbol store
* @param[in] name attribute name, only used for the duration of the call.
* @param[in] value value to give the binding
* @return error code, NIX_OK on success.
*/