either.h File Reference

A choice type with two cases. More...

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Macros
#define	ML99_left(x)   ML99_call(ML99_left, x)
	The left value x.
#define	ML99_right(x)   ML99_call(ML99_right, x)
	The right value x.
#define	ML99_isLeft(either)   ML99_call(ML99_isLeft, either)
	ML99_true() if either contains a left value, otherwise ML99_false().
#define	ML99_isRight(either)   ML99_call(ML99_isRight, either)
	The inverse of ML99_isLeft.
#define	ML99_eitherEq(cmp, either, other)   ML99_call(ML99_eitherEq, cmp, either, other)
	Tests either and other for equality.
#define	ML99_unwrapLeft(either)   ML99_call(ML99_unwrapLeft, either)
	Returns the left value on ML99_left(x) or emits a fatal error on ML99_right(y).
#define	ML99_unwrapRight(either)   ML99_call(ML99_unwrapRight, either)
	The inverse of ML99_unwrapLeft.
#define	ML99_LEFT(x)   ML99_CHOICE(left, x)
#define	ML99_RIGHT(x)   ML99_CHOICE(right, x)
#define	ML99_IS_LEFT(either)   ML99_PRIV_IS_LEFT(either)
#define	ML99_IS_RIGHT(either)   ML99_NOT(ML99_IS_LEFT(either))

Detailed Description

A choice type with two cases.

Macro Definition Documentation

ML99_eitherEq

#define ML99_eitherEq	(		cmp,
			either,
			other
	)		ML99_call(ML99_eitherEq, cmp, either, other)

Tests either and other for equality.

Examples

#include <metalang99/either.h>
#include <metalang99/nat.h>
 
// 1
ML99_eitherEq(v(ML99_natEq), ML99_left(v(123)), ML99_left(v(123)))
 
// 0
ML99_eitherEq(v(ML99_natEq), ML99_right(v(123)), ML99_left(v(8)))
 
// 0
ML99_eitherEq(v(ML99_natEq), ML99_right(v(123)), ML99_left(v(123)))

ML99_isLeft

#define ML99_isLeft

(

either

)

ML99_call(ML99_isLeft, either)

ML99_true() if either contains a left value, otherwise ML99_false().

Examples

#include <metalang99/either.h>
 
// 1
ML99_isLeft(ML99_left(v(123)))
 
// 0
ML99_isLeft(ML99_right(v(123)))

ML99_isRight

#define ML99_isRight

(

either

)

ML99_call(ML99_isRight, either)

The inverse of ML99_isLeft.

Examples

#include <metalang99/either.h>
 
// 1
ML99_isRight(ML99_right(v(123)))
 
// 0
ML99_isRight(ML99_left(v(123)))

ML99_unwrapLeft

#define ML99_unwrapLeft

(

either

)

ML99_call(ML99_unwrapLeft, either)

Returns the left value on ML99_left(x) or emits a fatal error on ML99_right(y).

Examples

#include <metalang99/either.h>
 
// 123
ML99_unwrapLeft(ML99_left(v(123)))
 
// Emits a fatal error.
ML99_unwrapLeft(ML99_right(v(123)))

ML99_unwrapRight

#define ML99_unwrapRight

(

either

)

ML99_call(ML99_unwrapRight, either)

The inverse of ML99_unwrapLeft.

Examples

#include <metalang99/either.h>
 
// 123
ML99_unwrapRight(ML99_right(v(123)))
 
// Emits a fatal error.
ML99_unwrapRight(ML99_left(v(123)))