In C, shift distances equal to or larger than the number of bits in the
operand result in undefined behaviour. As part of eliminating undefined
behaviour in arithmetic, mask off the distance like Java and JavaScript
specify and C on x86 usually does.
Assumption: conversion from unsigned to signed retains the two's complement
bits.
Assumption: uintmax_t has no padding bits.
The "exp" builtin is undocumented, non-standard and not very useful.
If exp's return value is not used, something like
VAR=$(exp EXPRESSION)
is equivalent to
VAR=$((EXPRESSION))
except that errors in the expression are fatal and quoting special
characters is not needed in the latter case.
If exp's return value is used, something like
if exp EXPRESSION >/dev/null
can be replaced by
if [ $((EXPRESSION)) -ne 0 ]
with similar differences.
The exp-run showed that "let" is close enough to bash's and ksh's builtin
that removing it would break a few ports. Therefore, "let" remains in 9.x.
PR: bin/104432
Exp-run done by: pav (with some other sh(1) changes)
Note that this only applies to variables that are actually used.
Things like (0 && unsetvar) do not cause an error.
Exp-run done by: pav (with some other sh(1) changes)
New features:
* proper lazy evaluation of || and &&
* ?: ternary operator
* executable is considerably smaller (8K on i386) because lex and yacc are
no longer used
Differences from dash:
* arith_t instead of intmax_t
* imaxdiv() not used
* unset or null variables default to 0
* let/exp builtin (undocumented, will probably be removed later)
Obtained from: dash
