struct argument

1.7 struct argument

An argument has the following structure:

struct argument {
        int arg_type;
        union {
                char *string;
                struct expression *exp;
        } u;
        struct argument *next;
};

arg_type

This member specifies the type of the argument. Table 1.7 shows its values.

u

This member represents for one specific type of argument. It can be a string, or an expression. Therefore, it is a union of two pointers, one to a string, and the other to an expression structure (see section1.4). Which pointer is active depends on the value of arg_type. Table 1.7 shows the rule.

next

This member is a pointer to the next argument in the list.

Table 1.7 Argument Types

Name	Value	Active Member in Union	Argument Data Structure
`STRING`	`0`	`u.string`	`a string`
`EXP`	`1`	`u.exp`	`an expression structure`

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