Section: Inspection Functions
y = exist(item,kind)
where item
is a string containing the name of the item
to look for, and kind
is a string indicating the type
of the search. The kind
must be one of
'builtin'
checks for built-in functions
'dir'
checks for directories
'file'
checks for files
'var'
checks for variables
'all'
checks all possibilities (same as leaving out kind
)
kind
specification out, in which case
the calling syntax is
y = exist(item)
The return code is one of the following:
item
does not exist
item
is a variable in the workspace
item
is an M file on the search path, a full pathname to a file, or an ordinary file on your search path
item
is a built-in FreeMat function
item
is a directory
1.10
, exist
used a different notion
of existence for variables: a variable was said to exist if it
was defined and non-empty. This test is now performed by isset
.
exist
function. Note that generally exist
is used in functions to test for keywords. For example,
function y = testfunc(a, b, c) if (~exist('c')) % c was not defined, so establish a default c = 13; end y = a + b + c;
An example of exist
in action.
--> a = randn(3,5,2) a = <double> - size: [3 5 2] (:,:,1) = Columns 1 to 3 -1.218553558434237294 -0.058665539142637134 1.035341956849705314 -0.499147758110993933 1.313015386207676327 0.491732208629773127 0.353746340101413204 0.561773300674407672 0.038771107253223712 Columns 4 to 5 0.972527520109172872 -0.727259104935995548 0.785593925641515534 -0.977203621921190591 -2.796089025580261289 -1.267146737297288217 (:,:,2) = Columns 1 to 3 1.032311919864423055 0.934652433302886942 -0.797640107843293311 0.735104330883378565 -0.078653779371251842 0.246197536758750335 -1.477029823428393618 -1.650750032221346197 -0.610267072493031359 Columns 4 to 5 0.784172706704981515 3.208972433336426011 -1.588329627273568523 0.579883457004424785 -1.514976216510938611 0.322389326974807544 --> b = [] b = <double> - size: [0 0] [] --> who Variable Name Type Flags Size a double [3 5 2] ans logical [1 1] b double [0 0] c int32 [1 3] f string [1 5] p double [1 256] x cell [2 1] y struct [1 1] --> exist('a') ans = <int32> - size: [1 1] 1 --> exist('b') ans = <int32> - size: [1 1] 1 --> exist('c') ans = <int32> - size: [1 1] 1