Check if int is between two numbers

Question

Why can t do you this if you try to find out whether an int is between to numbers   if 10  lt  x  lt  20    Instead of it  you ll have to do  if 10 lt x  amp  amp  x lt 20    which seems like a bit of overhead

User · Answer

Because the  lt  operator  and most others  are binary operators  they take two arguments   and  true true  is not a valid boolean expression   The Java language designers could have designed the language to allow syntax like the type you prefer  but  I m guessing  they decided that it was not worth the more complex parsing rules

User · Answer

Because that syntax simply isn t defined  Besides  x  lt  y evaluates as a bool  so what does bool  lt  int mean  It isn t really an overhead  besides  you could write a utility method if you really want - isBetween 10 x 20  - I wouldn t myself  but hey

User · Answer

The inconvenience of typing 10  lt  x  amp  amp  x  lt  20 is minimal compared to the increase in language complexity if one would allow 10  lt  x  lt  20  so the designers of the Java language decided against supporting it

User · Answer

if  10  lt  x    x  lt  20   This statement will evaluate true for numbers between 10 and 20  This is a rough equivalent to 10  lt  x  lt  20

User · Answer

You could make your own  public static boolean isBetween int a  int b  int c        return b  gt  a   c  gt  a  amp  amp  c  lt  b   c  gt  b  amp  amp  c  lt  a      Edit  sorry checks if c is between a and b

User · Answer

COBOL allows that  I am sure some other languages do as well    Java inherited most of it s syntax from C which doesn t allow it

User · Answer

You are human  and therefore you understand what the term  10  lt  x  lt  20  suppose to mean  The computer doesn t have this intuition  so it reads it as    10  lt  x   lt  20    For example  if x   15  it will calculate    10  lt  x     TRUE   TRUE  lt  20          In C programming  it will be worse  since there are no True False values  If x   5  the calculation will be   10  lt  x    0  the value of False   0  lt  20    non-0 number  True   and therefore  10  lt  5  lt  20  will return True   S

User · Answer

One problem is that a ternary relational construct would introduce serious parser problems    lt expr gt       lt expr gt   lt rel-op gt   lt expr gt                                 lt expr gt   lt rel-op gt   lt expr gt   lt rel-op gt   lt expr gt    When you try to express a grammar with those productions using a typical PGS  you ll find that there is a shift-reduce conflict at the point of the first  lt rel-op gt    The parse needs to lookahead an arbitrary number of symbols to see if there is a second  lt rel-op gt  before it can decide whether the binary or ternary form has been used   In this case  you could not simply ignore the conflict because that would result in incorrect parses   I m not saying that this grammar is fatally ambiguous   But I think you d need a backtracking parser to deal with it correctly   And that is a serious problem for a programming language where fast compilation is a major selling point

User · Answer

simplifying   a   10  b   15  c   20  public static boolean check int a  int b  int c        return a lt  b  amp  amp  b lt  c      This checks if b is between a and c

User · Answer

It s just the syntax     lt   is a binary operation  and most languages don t make it transitive   They could have made it like the way you say  but then somebody would be asking why you can t do other operations in trinary as well    if  12  lt  x    5     Syntax is always a trade-off between complexity  expressiveness and readability   Different language designers make different choices   For instance  SQL has  x BETWEEN y AND z   where x  y  and z can individually or all be columns  constants  or bound variables   And I m happy to use it in SQL  and I m equally happy not to worry about why it s not in Java

[java] Check if int is between two numbers

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