Type detection: Difference between revisions
→{{header|C}}
Line 129:
3 is a hexadecimal digit
</pre>
===Dispatch by tagged union===
<lang c>#include <stdio.h>
#include <stdbool.h>
#include <assert.h>
typedef enum {
STRING,
INPUT_FILE
} tag_t;
typedef struct {
tag_t tag;
union {
char *string;
FILE *input_file;
} value;
} source_t;
void
print_text (source_t source)
{
switch (source.tag)
{
case STRING:
fputs (source.value.string, stdout);
break;
case INPUT_FILE:
{
int c;
c = getc (source.value.input_file);
while (c != EOF)
{
putc (c, stdout);
c = getc (source.value.input_file);
}
}
break;
default:
assert (false);
}
}
int
main ()
{
source_t source;
source.tag = STRING;
source.value.string = "This\nis a\ntext.\n";
print_text (source);
source.tag = INPUT_FILE;
source.value.input_file = fopen ("type_detection-c.c", "r");
print_text (source);
}</lang>
{{out}}
$ cc type_detection-c.c && ./a.out
<pre>This
is a
text.
#include <stdio.h>
#include <stdbool.h>
#include <assert.h>
typedef enum {
STRING,
INPUT_FILE
} tag_t;
typedef struct {
tag_t tag;
union {
char *string;
FILE *input_file;
} value;
} source_t;
void
print_text (source_t source)
{
switch (source.tag)
{
case STRING:
fputs (source.value.string, stdout);
break;
case INPUT_FILE:
{
int c;
c = getc (source.value.input_file);
while (c != EOF)
{
putc (c, stdout);
c = getc (source.value.input_file);
}
}
break;
default:
assert (false);
}
}
int
main ()
{
source_t source;
source.tag = STRING;
source.value.string = "This\nis a\ntext.\n";
print_text (source);
source.tag = INPUT_FILE;
source.value.input_file = fopen ("type_detection-c.c", "r");
print_text (source);
}</pre>
=={{header|C sharp|C#}}==
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