Objective C: 18 is not greater than -1? -

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i have peculiar problem here. i'm building spider grab hyperlinks webpage , put them table , i'm using nsranges parse html document, i've run issue.

i have following line of code:

nslog(@"%lu", [datastring rangeofstring:@"contents.asp?year1" options:0 range:nsmakerange(index, datastring.length - index)].length);

this echoes 18 log, should, if put boolean statement, seeing if length greater -1:

nslog(@"%d", ([datastring rangeofstring:@"contents.asp?year1" options:0 range:nsmakerange(index, datastring.length - index)].length > -1));

this echoes 0, or false. 18 greater -1, what's problem? if switch < -1, returns true. have type-casting unsigned long?

here's the definition of nsrange:

typedef struct _nsrange {       nsuinteger location;       nsuinteger length; } nsrange;

notice both fields of type nsuinteger, unsigned type. in fact, nsuinteger unsigned long.

since there no wider integer type unsigned long, compiler promotes -1 unsigned. can't recall whether undefined behavior, on ios , mac os x has effect of treating 2's complement bit pattern of -1 unsigned integer. bit pattern, unsigned integer, maximum unsigned integer value.

thus comparison can never true.

if think -1 means "not found", mistaken. correct way check whether rangeofstring:options:range: failed find target check whether location of returned range nsnotfound:

nsuinteger location = [datastring rangeofstring:@"contents.asp?year1"     options:0 range:nsmakerange(index, datastring.length - index)].location bool foundit = location != nsnotfound;

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