Methods

show

int show(var self);
int show_to(var self, var out, int pos);

Show the object self either to stdout or to the object output.

look

int look(var self);
int look_from(var self, var input, int pos);

Read the object self either from stdout or from the object input.

print

#define print(fmt, ...)
#define println(fmt, ...)
#define print_to(out, pos, fmt, ...)
int print_with(const char* fmt, var args);
int println_with(const char* fmt, var args);
int print_to_with(var out, int pos, const char* fmt, var args);

Print the format string fmt either to stdout or to the object out at positions pos. Returns new position in output.

scan

#define scan(fmt, ...)
#define scanln(fmt, ...)
#define scan_from(input, pos, fmt, ...)
int scan_with(const char* fmt, var args);
int scanln_with(const char* fmt, var args);
int scan_from_with(var input, int pos, const char* fmt, var args);

Scan the format string fmt either from stdout or from the object input at position pos. Returns new position in output.

Examples

Hello World

println("Hello %s!", $S("World"));

File Writing

with (f in new(File, $S("prices.txt"), $S("wb"))) {
  print_to(f, 0, "%$ :: %$\n", $S("Banana"), $I(57));
  print_to(f, 0, "%$ :: %$\n", $S("Apple"),  $I(22));
  print_to(f, 0, "%$ :: %$\n", $S("Pear"),   $I(16));
}

String Scanning

var input = $S("1 and 52 then 78");

var i0 = $I(0), i1 = $I(0), i2 = $I(0);
scan_from(input, 0, "%i and %i then %i", i0, i1, i2);

/* i0: 1, i1: 52, i2: 78 */
println("i0: %$, i1: %$, i2: %$", i0, i1, i2);

String Printing

var greeting = new(String);
print_to(greeting, 0, "Hello %s %s, %s?", 
  $S("Mr"), $S("Johnson"), $S("how are you?"));

/* Hello Mr Johnson, how are you? */
show(greeting);

Show

Convert To or From String

The Show class is used to convert objects to, and from, a String representation. Objects which implement Show should expect the input/output object to be one that support the Format class, such as File or String.

The print, println and print_to functions provide a mechanism for writing formatted strings with Cello objects. To do this they provide a new format specifier %$ which uses an object's Show functionality to write that part of the string. All objects which don't support Show can still be shown via a default implementation.

All the Show methods which are variable arguments only take var objects as input. To print native C types wrap them in Cello types using $.

Standard format specifiers such as %f and %d will call functions such as c_float and c_int on their passed arguments to convert objects to C types before performing the standard C formatting behaviour.

See printf for more information on format specifiers.

Definition

struct Show {
  int (*show)(var, var, int);
  int (*look)(var, var, int);
};

Implementers

Array | Sequential Container
Box | Unique Pointer
Exception | Exception Object
Float | Floating Point Object
GC | Garbage Collector
Int | Integer Object
List | Linked List
Range | Integer Sequence
Slice | Partial Iterable
String | String Object
Table | Hash table
Tree | Balanced Binary Tree
Tuple | Basic Collection
Type | Metadata Object

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Cello High Level C

Methods

Examples

Show

Definition

Implementers