Library Functions

Scheme_Object *scheme_get_param(Scheme_Config *config, int param_id) 

Gets the current value of the parameter specified by param_id. (This is a macro.)

Scheme_Object *scheme_get_param_or_null(Scheme_Config *config, int param_id) 

Gets the current value of the parameter specified by param_id. (This is a macro.)

Scheme_Object *scheme_make_config(Scheme_Config *base) 

Creates and returns a new configuration, using base as the base configuration. If base is NULL, the current thread's parameterization's current base parameterization is used.

int scheme_new_param() 

Allocates a new primitive parameter index. This function must be called before scheme_basic_env.

Scheme_Object *scheme_make_parameter(Scheme_Prim *function, char *name) 

Use this function instead of the other primitive-constructing functions, like scheme_make_prim, to create a primitive parameter procedure. See also scheme_param_config, below.

Scheme_Object *scheme_param_config( char *name, long param_id, int argc, Scheme_Object **argv,
               int arity, Scheme_Prim *check, char *expected, int isbool) 

Call this procedure in a primitive parameter procedure to implement the work of getting or setting the parameter. The name argument should be the parameter procedure name; it is used to report errors. The param_id argument is the primtive parameter index returned by scheme_new_param. The argc and argv arguments should be the un-touched and un-tested arguments that were passed to the primitive parameter (the implementation of in-parameterization will do strange things to these arguments). Argument-checking is performed within scheme_param_config using arity, check, expected, and isbool:

• If arity is non-negative, potential parameter values must be able to accept the specified number of arguments. The check and expected arguments should be NULL.
• If check is not NULL, it is called to check a potential parameter value. The arguments passed to check are always 1 and an array that contains the potential parameter value. If isbool is 0 and check returns scheme_false, then a type error is reported using name and expected. If isbool is 1, then a type error is reported only when check returns NULL and any non-NULL return value is used as the actual value to be stored for the parameter.
• Otherwise, isbool should be 1. A potential procedure argument is then treated as a Boolean value.