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This documents describes parts of the YSH language that may be surprising.
All languages have warts, but most of them don't document them for you! Even a
nice language like Python has surprising cases like 42,
and f(x),
being a
1-tuple (because of the trailing comma).
The goal of YSH is to remove the many warts of shell, documented at Shell WTFs. Nonetheless it has some of its own.
No:
if ((x + 1) < n) { # note ((
echo 'less'
}
Yes:
if ( (x + 1) < n) { # add a space
echo 'less'
}
This is because the ((
token is for bash arithmetic, which is disallowed in
YSH.
Block
and Expr
LiteralsBlocks look different in command vs expression mode:
cd /tmp { # command mode { }
echo $PWD
}
var myblock = ^(echo $PWD) # expression mode, lazy ^( )
So do expressions:
myproc | where (age > 10) # command mode, lazy ( )
var myval = age > 10 # expression mode
var myexpr = ^[age > 10] # expression mode, lazy ^[ ]
It would have been nicer if they were consistent, but shell is already
inconsistent with $(echo hi)
and { echo hi; }
.
There is consistency in other directions:
^(echo $PWD)
is consistent with shell's eagerly evaluated $(echo $PWD)
.^[42 + f(x)]
is consistent with expression sub $[42 + f(x)]
.Most users won't see these literal forms very much. They're more useful for testing and frameworks rather than simple scripts/applications.