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73 lines
2.9 KiB
Text
73 lines
2.9 KiB
Text
texinode(Arithmetic Evaluation)(Conditional Expressions)(Jobs & Signals)(Top)
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chapter(Arithmetic Evaluation)
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ifzman(\
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sect(Arithmetic Evaluation)
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)\
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cindex(arithmetic evaluation)
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cindex(evaluation, arithmetic)
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An ability to perform integer arithmetic is provided with the builtin tt(let).
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findex(let, use of)
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Evaluations are performed using em(long) arithmetic.
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A leading `tt(0x)' or `tt(0X)' denotes hexadecimal.
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Otherwise, numbers are of the form `[var(base)tt(#)]var(n)',
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where var(base) is a decimal number between two and thirty-six
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representing the arithmetic base and var(n)
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is a number in that base (for example, `tt(16#ff)' is 255 in hexadecimal).
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If var(base) is omitted
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then base 10 is used. For backwards compatibility the form
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`tt([)var(base)tt(])var(n)' is also accepted.
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cindex(arithmetic operators)
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cindex(operators, arithmetic)
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An arithmetic expression uses nearly the same syntax, precedence, and
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associativity of expressions in C.
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The following operators are supported (listed in decreasing order
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of precedence):
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startsitem()
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sitem(tt(PLUS() - ! ~ PLUS()PLUS() --))(unary plus/minus, logical NOT, complement, {pre,post}{in,de}crement)
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sitem(tt(<< >>))(bitwise shift left, right)
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sitem(tt(&))(bitwise AND)
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sitem(tt(^))(bitwise XOR)
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sitem(tt(|))(bitwise OR)
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sitem(tt(**))(exponentiation)
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sitem(tt(* / %))(multiplication, division, modulus (remainder))
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sitem(tt(PLUS() -))(addition, subtraction)
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sitem(tt(< > <= >=))(comparison)
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sitem(tt(== !=))(equality and inequality)
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sitem(tt(&&))(logical AND)
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sitem(tt(|| ^^))(logical OR, XOR)
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sitem(tt(? :))(ternary operator)
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sitem(tt(= PLUS()= -= *= /= %= &= ^= |= <<= >>= &&= ||= ^^= **=))(assignment)
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sitem(tt(,))(comma operator)
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endsitem()
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The operators `tt(&&)', `tt(||)', `tt(&&=)', and `tt(||=)' are short-circuiting,
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and only one of the latter two expressions in a ternary operator
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is evaluated. Note the precedence of the bitwise AND, OR,
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and XOR operators.
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An expression of the form `tt(#\)var(x)' where var(x) is any character
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gives the ascii value of this character and an expression of the form
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`tt(#)var(foo)' gives the ascii value of the first character of the value
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of the parameter var(foo).
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Named parameters and subscripted arrays can be referenced by name within an
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arithmetic expression without using the parameter substitution syntax.
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An internal integer representation of a named parameter
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can be specified with the tt(integer) builtin.
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cindex(parameters, integer)
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cindex(integer parameters)
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findex(integer, use of)
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Arithmetic evaluation is performed on the value of each
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assignment to a named parameter declared integer
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in this manner.
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Since many of the arithmetic operators require
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quoting, an alternative form of the tt(let) command is provided.
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For any command which begins with a tt(LPAR()LPAR()),
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all the characters until a matching tt(RPAR()RPAR())
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are treated as a quoted expression.
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More precisely, `tt(LPAR()LPAR()) ... tt(RPAR()RPAR())'
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is equivalent to `tt(let ")...tt(")'.
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