7.5 Type testing

To check whether a given OZ_Term is a certain Oz value several functions are provided:

OZ_isAtom

OZ_isBool

OZ_isCell

OZ_isThread

OZ_isPort

OZ_isChunk

OZ_isDictionary

OZ_isCons

OZ_isFalse

OZ_isFeature

OZ_isFloat

OZ_isInt

OZ_isBigInt

OZ_isSmallInt

OZ_isNumber

OZ_isLiteral

OZ_isName

OZ_isNil

OZ_isObject

OZ_isPair

OZ_isPair2

OZ_isProcedure

OZ_isRecord

OZ_isTrue

OZ_isTuple

OZ_isUnit

OZ_isValue

OZ_isVariable

OZ_isBitString

OZ_isByteString

OZ_isFSetValue

All these functions have the same signature. For example OZ_isAtom is declared as int OZ_isAtom(OZ_Term t)

All type tests return nonzero iff their argument is of the respective type.

A few of these need some more explanation:

int OZ_isBigInt(OZ_Term t)
int OZ_isSmallInt(OZ_Term t)

The emulator has two representations for integers: small integers and big integers. Small integers are implemented very efficiently.

int OZ_isPair(OZ_Term t)

Returns zero iff t is a tuple with label #.

int OZ_isPair2(OZ_Term t)

Returns nonzero iff t is a tuple with label # and arity of 2.

int OZ_isValue(OZ_Term t)

Returns nonzero iff t is not a variable.

int OZ_isVariable(OZ_Term t)

Returns nonzero iff t is a variable.

OZ_isList

int OZ_isList(OZ_Term term, OZ_Term *var)

Returns nonzero iff term is a list. If term is no list, but the tail is a variable, then *var is set to the tail of the list, else it is set to null. var may be null. If term is cyclic then OZ_isList never terminates!

OZ_isString

int OZ_isString(OZ_Term term, OZ_Term *var)

Returns nonzero iff term is an Oz string. If term is no string, but the tail or an element of the list is a variable, then *var is set to this variable, else it is set to null. var may be null. If term is cyclic then OZ_isString never terminates!

OZ_isVirtualString

int OZ_isVirtualString(OZ_Term term, OZ_Term *var)

Returns nonzero iff term is a virtual string. If term is no virtual string, but contains a variable, then *var is set to this variable, else it is set to null. var may be null. If term is cyclic then OZ_isVirtualString never terminates!

OZ_termType

OZ_Term OZ_termType(OZ_Term t)

Returns an atom describing the type of t. The following types are returned:

variable, int, float, atom, name, tuple, record, fset,
foreignPointer, procedure, cell, space, object, port,
chunk, array, dictionary, lock class, resource

(see also Value.type in Section 3.2 of ``The Oz Base Environment'').